Unit 10 (Electricity)

Electrolysis

Friday April 5, 2019

This experiment is just for advanced students. If you guessed that this has to do with electricity and chemistry, you’re right! But you might wonder how they work together. Back in 1800, William Nicholson and Johann Ritter were the first ones to split water into hydrogen and oxygen using electrolysis. (Soon afterward, Ritter went on to figure out electroplating.) They added energy in the form of an electric current into a cup of water and captured the bubbles forming into two separate cups, one for hydrogen and other for oxygen.

This experiment is not an easy one, so feel free to skip it if you need to. You don’t need to do this to get the concepts of this lesson but it’s such a neat and classical experiment (my students love it) so you can give it a try if you want to. The reason I like this is because what you are really doing in this experiment is ripping molecules apart and then later crashing them back together.

Have fun and please follow the directions carefully. This could be dangerous if you’re not careful. The image shown here is using graphite from two pencils sharpened on both ends, but the instructions below use wire. Feel free to try both to see which types of electrodes provide the best results.

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You will need:

2 test tubes or thin glass or plastic something closed at one end. I do not recommend anything wider than a half inch in diameter.
2 two wires, one needs to be copper, at least 12 inches long. Both wires need to have bare ends.
1 Cup
Water
One 9 volt battery
Long match or a long thin piece of wood (like a popsicle stick) and a match
Rubber bands
Masking tape
Salt

Download Student Worksheet & Exercises
1. Fill the cup with water.

2. Put a tablespoon or so of salt into the water and stir it up. (The salt allows the electricity to flow better through the water.)

2. Put one wire into the test tube and rubber band it to the test tube so that it won’t come out (see picture).

3. Use the masking tape to attach both wires to the battery. Make sure the wire that is in the test tube is connected to the negative (-) pole of the battery and that the other is connected to the positive (+) pole. Don’t let the bare parts of the different wires touch. They could get very hot if they do.

4. Fill the test tube to the brim with the salt water.

5. This is the tricky part. Put your finger over the test tube, turn it over and put the test tube, open side down, into the cup of water. (See picture.)

6. Now put the other wire into the water. Be careful not to let the bare parts of the wires touch.

7. You should see bubbles rising into the test tube. If you don’t see bubbles, check the other wire. If bubbles are coming from the other wire either switch the wires on the battery connections or put the wire that is bubbling into the test tube and remove the other. If you see no bubbles check the connections on the battery.

8. When the test tube is half full of gas (half empty of salt water depending on how you look at it) light the long match or the wooden stick. Then take the test tube out of the water and let the water drain out. Holding the test tube with the open end down, wait for five seconds and put the burning stick deep into the test tube (the flame will probably go out but that’s okay). You should hear an instant pop and see a flash of light. If you don’t, light the stick again and try it another time. For some reason, it rarely works the first time but usually does the second or third.

A water molecule, as you saw before, is two hydrogen atoms and one oxygen atom. The electricity encouraged the oxygen to react with the copper wire leaving the hydrogen atoms with no oxygen atom to hang onto. The bubbles you saw were caused by the newly released hydrogen atoms floating through the test tube in the form of hydrogen gas. Eventually that test tube was part way filled with nothing but pure hydrogen gas.

But how do you know which bubbles are which? You can tell the difference between the two by the way they ignite (don’t’ worry – you’re only making a tiny bit of each one, so this experiment is completely safe to do with a grown up).

It takes energy to split a water molecule. (On the flip side, when you combine oxygen and hydrogen together, it makes water and a puff of energy. That’s what a fuel cell does.) Back to splitting the water molecule - as the electricity zips through your wires, the water molecule breaks apart into smaller pieces: hydrogen ions (positively charged hydrogen) and oxygen ions (negatively charged oxygen). Remember that a battery has a plus and a minus charge to it, and that positive and negative attract each other.

So, the positive hydrogen ions zip over to the negative terminal and form tiny bubbles right on the wire. Same thing happens on the positive battery wire. After a bit of time, the ions form a larger gas bubble. If you stick a cup over each wire, you can capture the bubbles and when you’re ready, ignite each to verify which is which.

If the match burns brighter, the gas is oxygen. If you hear a POP!, the gas is hydrogen. Oxygen itself is not flammable, so you need a fuel in addition to the oxygen for a flame. In one case, the fuel is hydrogen, and hence you hear a pop as it ignites. In the other case, the fuel is the match itself, and the flame glows brighter with the addition of more oxygen.

When you put the match to it, the energy of the heat causes the hydrogen to react with the oxygen in the air and “POP”, hydrogen and oxygen combine to form what? That’s right, more water. You have destroyed and created water! (It’s a very small amount of water so you probably won’t see much change in the test tube.)

The chemical equations going on during this electrolysis process look like this:

A reduction reaction is happening at the negatively charged cathode. Electrons from the cathode are sticking to the hydrogen cations to form hydrogen gas:

2 H⁺_(aq) + 2e^- --> H_2(g)

2 H₂O_(l) + 2e^- --> H_2(g) + 2 OH^-_(aq)

The oxidation reaction is occurring at the positively charged anode as oxygen is being generated:

2 H₂O_(l) --> O_2(g) + 4 H⁺_(aq) + 4e^-

4 OH^-_(aq) --> O_2(g) + 2 H₂O_(l) + 4 e-

Overall reaction:

2 H₂O_(l) --> 2 H_2(g) + O_2(g)

Note that this reaction creates twice the amount of hydrogen than oxygen molecules. If the temperature and pressure for both are the same, you can expect to get twice the volume of hydrogen to oxygen gas (This relationship between pressure, temperature, and volume is the Ideal Gas Law principle.)

This is the idea behind vehicles that run on sunlight and water. They use a solar panel (instead of a 9V battery) to break apart the hydrogen and oxygen and store them in separate tanks, then run them both back together through a fuel cell, which captures the energy (released when the hydrogen and oxygen recombine into water) and turns the car's motor. Cool, isn't it?

Note: We're going to focus on Alternative Energy in Unit 12 and create all sorts of various energy sources including how to make your own solar battery, heat engine, solar & fuel cell vehicles (as described above), and more!

Exercises

Why are bubbles forming?
Did bubbles form at both wires, or only one? What kind of bubbles are they?
What would happen if you did this experiment with plain water? Would it work? Why or why not?
Which terminal (positive or negative) produced the hydrogen gas?
Did the reaction create more hydrogen or more oxygen?

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Advanced Static Lab

Friday April 5, 2019

If you have a Fun Fly Stick, then pull it out and watch the video below. If not, don't worry - you can do most of these experiments with a charged balloon (one that you've rubbed on your hair). Let' play with a more static electricity experiments, including making things move, roll, spin, chime, light up, wiggle and more using static electricity! [am4show have='p8;p9;p97;p58;' guest_error='Guest error message' user_error='User error message' ] Materials:

sheet of paper
two empty, clean soup cans
aluminum foil
long straight pin
three film canisters (or M&M containers or small plastic bottles)
penny
neon bulb (optional)
small styrofoam ball or single packing peanut
fishing line or thread
chopstick
foam cup
small aluminum pie tins or make your own from aluminum foil
hot glue with glue sticks
Fun Fly Stick (also called "Wonder Fly Stick")

This video show you how to get the most out of your Fun Fly Stick. If you don't have a Fly Stick, simply use an inflated balloon that you've rubbed on your head. In the video, the Electrostatic Lab is mounted on a foam meat tray I found at the grocery store.

Download Student Worksheet & Exercises The triboelectric series is a list that ranks different materials according to how they lose or gain electrons. Near the top of the list are materials that take on a positive charge, such as air, human skin, glass, rabbit fur, human hair, wool, silk, and aluminum. Near the bottom of the list are materials that take on a negative charge, such as amber, rubber balloons, copper, brass, gold, cellophane tape, Teflon, and silicone rubber. When you turn on your Fun Fly Stick (or rub your head with a balloon), one end of the Fun Fly Stick takes on a positive charge and the other end holds the negative charge. When you rub your head with a balloon, the hair takes on a positive charge and the balloon takes on a negative charge. When you scuff along the carpet, you build up a static charge (of electrons). Your socks insulate you from the ground, and the electrons can’t cross your sock-barrier and zip back into the ground. When you touch someone (or something grounded, like a metal faucet), the electrons jump from you and complete the circuit, sending the electrons from you to them (or it). Exercises

What is common throughout all these experiments that make them work?
What makes the neon bulb light up? What else would work besides a neon bulb?
Does it matter how far apart the soup cans are?
Why does the foil ball go back and forth between the two cans?
Why do the pans take on the same charge as the Fly Stick?
When sticking a sheet of paper to the wall, does it matter how long you charge the paper for?
Draw a diagram to explain how the electrostatic motor works. Label each part and show where the charges are and how they make the rotor turn.

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Electric Eye Sensor

Friday April 5, 2019

This is a super-cool and ultra-simple circuit experiment that shows you how a CdS (cadmium sulfide cell) works. A CdS cell is a special kind of resistor called a photoresistor, which is sensitive to light.

A resistor limits the amount of current (electricity) that flows through it, and since this one is light-sensitive, it will allow different amounts of current through depends on how much light it “sees”.

Photoresistors are very inexpensive light detectors, and you’ll find them in cameras, street lights, clock radios, robotics, and more. We’re going to play with one and find out how to detect light using a simple series circuit.

Materials:

AA battery case with batteries
one CdS cell
three alligator wires
LED (any color and type)

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Download Student Worksheet & Exercises

Exercises

How is a CdS cell like a switch? How is it not like a switch?
When is the LED the brightest?
How could you use this as a burglar alarm?

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Pressure Sensor

Wednesday April 15, 2015

By controlling how and when a circuit is triggered, you can easily turn a simple circuit into a burglar alarm – something that alerts you when something happens. By sensing light, movement, weight, liquids, even electric fields, you can trigger LEDs to light and buzzers to sound. Your room will never be the same.

Switches control the flow of electricity through a circuit. There are different kinds of switches. NC (normally closed) switches keep the current flowing until you engage the switch. The SPST and DPDT switches are NO (normally open) switches.

The pressure sensor we’re building is small, and it requires a fair amount of pressure to activate. Pressure is force (like weight) over a given area (like a footprint). If you weighed 200 pounds, and your footprint averaged 10” long and 2” wide, you’d exert about 5 psi (pounds per square inch) per foot.

However, if you walked around on stilts indeed of feet, and the ‘footprint’ of each stilt averaged 1” on each side, you’d now exert 100 psi per foot. Why such a difference?

The secret is in the area of the footprint. In our example, your foot is about 20 square inches, but the area of each stilt was only 1 square inch. Since you haven’t changed your weight, you’re still pushing down with 200 pounds, only in the second case, you’re pressing the same weight into a much smaller spot… and hence the pressure applied to the smaller area shoots up by a factor of 20.

So how do we use pressure in this experiment? When you squeeze the foam, the light bulb lights up! It’s ideal for under a doormat or carpet rug where lots of weight will trigger it.

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Here’s what you need:

thin sponge or foam square (about 1″ square)
AA battery case
2 AA batteries
3 alligator clip wires
2 large paper clips
scissors
aluminum foil
buzzer or LED

Download Student Worksheet & Exercises

Troubleshooting: There are a few problem areas to watch out for when building this sensor. First, make sure the hole in your foam is big enough to stick a finger (or thumb) easily through. The foam keeps the foil apart until stepped on, then it squishes together to allow the foil to make contact through the hole.

The second potential problem is if the switch doesn’t turn the buzzer off. If this happens, it means you’re bypassing the switch entirely and keeping the circuit in the constant ON position. Check the two foil squares – are they touching around the outside edges? Lastly, make sure your foam is the kind that pops back into shape when released. (Thin sponges can work in a pinch.)

What’s happening? You’ve made a switch, only this one is triggered by squeezing it. If you’re using the special black foam without the hole, it works because the foam conducts more electricity when squished together, and less when it’s at the normal shape.

First, the special black foam is conducting some (but not enough) electricity when you squeeze it. It’s just the nature of the black foam included with the materials kit. Second, when you squeeze it, you’re getting the two foil squares to touch through the hole, and this is what really does it for your LED. When you release it, the foil spreads apart again because they are on opposite sides of the foam square.

Bonus Idea: Stick just the sensor under a rug and run longer wires from the sensor to your room. When someone comes down the hallway, they’ll trigger the sensor and alert you before they get there!

Exercises

How does this sensor work?
What makes this an NO switch?
How can you use both the trip wire and the pressure sensor in the same circuit? Draw it out here:

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Electroscope

Wednesday November 5, 2014

When high energy radiation strikes the Earth from space, it’s called cosmic rays. To be accurate, a cosmic ray is not like a ray of sunshine, but rather is a super-fast particle slinging through space. Think of throwing a grain of sand at a 100 mph… and that’s what we call a ‘cosmic ray’. Build your own electroscope with this video!

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Materials:

Clean glass jar with a lid
Wire coat hanger and sand paper
Aluminum foil
Vice grips or a hacksaw
Scissors
Balloon or other object to create a static charge
Hot glue gun (optional)

Download Student Worksheet & Exercises

Troubleshooting: This device is also known as an electroscope, and its job is to detect static charges, whether positive or negative. The easiest way to make sure your electroscope is working is to rub your head with a balloon and bring it near the foil ball on top – the foil “leaves” inside the jar should spread apart into a V-shape.

Exercises

How does this detector work?
Do all particles leave the same trail?
What happens when the magnet is brought close to the jar?

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Special Science Teleclass: Robotics

Monday November 3, 2014

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I've included it here so you can participate and learn, too!

Spark together electric motors, build homemade burglar alarms, wire up circuits and build your own robot from junk! Create your own whizzing, hopping, dancing, screeching, swimming, crawling, wheeling, robot during class. We'll cover hot topics in electricity, magnetism, electrical charges, robot construction, sensors and more.

[am4show have='p8;p9;p98;p11;p38;' guest_error='Guest error message' user_error='User error message' ] Materials:

AA battery case (Jameco 216081)
Two AA batteries for your battery case**
A couple of LEDs (You can use any under 3V, but if you need recommendations, try Jameco 2-lead LEDs or 3-lead LEDs)
Set of 10 alligator wires (Jameco 10444)
One or two 1.5-3V DC motors (Jameco 231925)
Index card
6 brass fasteners
Two large paper clips
One foam block (2” cube or larger)
1 wooden clothespin
10 wooden skewers
Drill & bit the size of the motor shaft diameter
Hot glue gun, razor and adult assistant
OPTIONAL: Buzzer (Jameco 24872)

**Note about batteries: The cheap dollar-store kind labeled “Heavy Duty” are recommended. Do not use alkaline batteries like "Duracell" or "Energizer" for your experiments with us during this class. (We'll explain during the class.)

Download the worksheet for this teleclass HERE.

Key Concepts

A robot not only moves but it can also interact with its environment and it does that by using sensors, like light detectors that can see light, you can have motion detectors that can sense movement, touch sensors, pressure sensors, infrared light sensors, proximity sensors, water detectors, spit sensors, detecting all different kinds of stuff!

Robots need electricity to make the motors move, the LEDs light up, the buzzers to sound, and more. When you move electrons around, that’s what creates the electricity. When you rub a balloon on your head for example, you’re picking off the electrons from the atoms in your hair and sticking them on the balloon. There's a static charge on your head due to the extra electrons.

The electrons have a negative charge, and so just like the north and south poles of a magnet attract each other, the negative charge of the electron is attracted to positive charges. That’s why your batteries have plus and minus signs on them. Electricity is when the electric charge is moving around inside the wires in the circuit.

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Special Science Teleclass: Electricity

Monday October 13, 2014

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too!

We’re going to study electrons and static charge. Kids will build simple electrostatic motor to help them understand how like charges repel and opposites attract. After you’ve completed this teleclass, be sure to hop on over the teleclass in Robotics!

Electrons are strange and unusual little fellows. Strange things happen when too many or too few of the little fellows get together. Some things may be attracted to other things or some things may push other things away. Occasionally you may see a spark of light and sound. The light and sound may be quite small or may be as large as a bolt of lightning. When electrons gather, strange things happen. Those strange things are static electricity.

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Materials:

Balloon (7-9″, inflated with air, not helium)
AA battery case
2 AA batteries for your battery case (cheap dollar-store “heavy duty” type are perfect. Don’t use alkaline batteries if you can help it, because kids are going to short circuit their circuits, and the cheaper kind are safer in case they do.)
1-2 LEDs
Alligator wires
1.5-3V DC motor
3-6V buzzer

If you want to make the laser burglar alarm, then get these also:

OPTIONAL: CdS Photoresistor for the laser burglar alarm
OPTIONAL: 9V Battery for laser burglar alarm
OPTIONAL: Laser pointer (the cheap kind from the dollar store work great) or strong flashlight for the laser burglar alarm

If you want to make the first robotics projects then also get these:

OPTIONAL: block of foam (any kind will do that is at least 2″ on each side)
OPTIONAL: 10 (or more) wood skewers at least 4″ long
OPTIONAL: 1 wood clothespin
OPTIONAL: Hot glue and glue sticks (with adult help)

If you want to make the second robotics project then also get these:

OPTIONAL: Additional 3V DV motor (you need two for this project)
OPTIONAL: 6 large popsicle sticks (tongue depressor size)
OPTIONAL: Tack or other sharp object for poking holes
OPTIONAL: Hot glue and glue sticks (with adult help)

Key Concepts

The proton has a positive charge, the neutron has no charge (neutron, neutral get it?) and the electron has a negative charge. These charges repel and attract one another kind of like magnets repel or attract. Like charges repel (push away) one another and unlike charges attract one another. Generally things are neutrally charged. They aren’t very positive or negative, rather have a balance of both.

Things get charged when electrons move. Electrons are negatively charged particles. So if an object has more electrons than it usually does, that object would have a negative charge. If an object has less electrons than protons (positive charges), it would have a positive charge. How do electrons move? It turns out that electrons can be kind of loosey goosey.

Depending on the type of atom they are a part of, they are quite willing to jump ship and go somewhere else. The way to get them to jump ship is to rub things together. Like in our experiment we’re about to do…

What’s Going On?

In static electricity, electrons are negatively charged and they can move from one object to another. This movement of electrons can create a positive charge (if something has too few electrons) or a negative charge (if something has too many electrons). It turns out that electrons will also move around inside an object without necessarily leaving the object. When this happens the object is said to have a temporary charge.

When you rub a balloon on your head, the balloon is now filled up with extra electrons, and now has a negative charge. Opposite charges attract right? So, is the entire yardstick now an opposite charge from the balloon? No. In fact, the yardstick is not charged at all. It is neutral. So why did the balloon attract it?

The balloon is negatively charged. It created a temporary positive charge when it got close to the yardstick. As the balloon gets closer to the yardstick, it repels the electrons in the yardstick. The negatively charged electrons in the yardstick are repelled from the negatively charged electrons in the balloon.

Since the electrons are repelled, what is left behind? Positive charges. The section of yardstick that has had its electrons repelled is now left positively charged. The negatively charged balloon will now be attracted to the positively charged yardstick. The yardstick is temporarily charged because once you move the balloon away, the electrons will go back to where they were and there will no longer be a charge on that part of the yardstick.

This is why plastic wrap, Styrofoam packing popcorn, and socks right out of the dryer stick to things. All those things have charges and can create temporary charges on things they get close to.

Questions to Ask

Does the shape of the balloon matter? Does hair color matter?
What happens if you rub the balloon on other things, like a wool sweater?
If you position other people with charged balloons around the table, can you keep the yardstick going?
Can we see electrons?
How do you get rid of extra electrons?
Rub a balloon on your head, and then lift it up about 5 inches. Why is the hair attracted to the balloon?
Why does the hair continue to stand on end after the balloon is taken away?
Why do you think the yardstick moved?
What other things are attracted or repelled the same way by the balloon? (Hint: try a ping pong ball.)

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Cosmic Ray Detector

Thursday August 1, 2013

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Materials:

Clean glass jar with a lid
Wire coat hanger and sand paper
Aluminum foil
Vice grips or a hacksaw
Scissors
Balloon or other object to create a static charge
Hot glue gun (optional)

Download Student Worksheet & Exercises

Exercises

How does this detector work?
Do all particles leave the same trail?
What happens when the magnet is brought close to the jar?

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Amphibious Robot

Tuesday June 14, 2011

Amphibious vehicles is a craft which travels on both land and water. And it doesn't need to be limited to just cars. There are amphibious bicycles, buses, and RVs. Hovercraft are amphibious, too!

Amphibious crafts started back in the 1800s as steam-powered barges. In the 1950s, the German Schimmwagen was a small jeep that could travel in water as well as on land. The most popular amphibious vehicle on the market is the 1960 Amphibicar (photo shown left) and later the Gibbs Aquada.

The secret to making an amphibious vehicle is this: it must be designed so it floats in water (it must be watertight and buoyant) and robust enough to travel on land. Many amphibious creations either leaked, sank, or never made it off the drawing board. But that's what being a scientist is all about: coming up with an overall goal and figuring out a way to overcome the problems faced along the way.

We're going to build our own version using items like foam blocks and hobby motors. Are you ready?
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Materials:

foam block (at least 2" x 6")
propeller
straw
two wood skewers
four wheels (tops from milk jugs, yogurt containers, etc)
3V DC motor
propeller
2 alligator clip leads
AA battery case with 2 AA batteries
hot glue gun
scissors

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Propeller Car

Monday May 31, 2010

The great news is that many of the problematic airplane troubles were figured out a long time ago by two amazing people: the Wright brothers.

The Wright brothers also took an airfoil (a fancy word for “airplane wing”), turned it sideways, and rotated it around quickly to produce the first real propeller that could generate an efficient amount of thrust to fly an aircraft.

Before the Wright brothers perfected the airfoil, people had been using the same “screw” design created by Archimedes in 250 BC. This twist in the propeller was such a superior design that modern propellers are only 5% more efficient than those created a hundred years ago by the two brilliant Wright brothers.

We’re going to use a propeller on our basic race car chassis (frame) to see how much thrust we’d need to make it move. If you don’t want to make the fancy triangle-shaped body frame, you can substitute a foam block or two (which will make your car able to go in water, too!)

Are you ready?
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Materials:

4 popsicle sticks
2 straws
4 wheels or lids from film canisters, or milk jug lids (anything plastic, round, and about the size of a quarter)
1 propeller
2 skewers
1 film can or foam block
3VDC motor
AA battery case with AA batteries
2 alligator clip lead wires
hot glue gun with glue sticks

Need help finding propellers? Rip one off an old fan or toy airplane, such as a balsa flyer.

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Bristle Brush Bot

Saturday May 1, 2010

This is the simplest robot you can make… out of old parts from around the house. While this little robot doesn’t use energy from the sun or wind, we’ve placed it here with other alternative energy projects because the parts come from the trash bin.

This project is an extension of the Jigglebot robot from Unit 10.

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You’ll need to find:

Old toothbrush you can destroy
Tiny vibrator motor (you can rip one out of an old cell phone) – just make sure it’s got a weight attached to the motor shaft.
Small watch battery (make sure it’s around 3V to match the motor)
Scissors and/or razor
Tape and a hot glue gun
Optional: Paper clips for claws and feet

Here’s what you do:

What’s going on? Your BristleBot uses the toothbrush bristles as legs and an eccentric motor to shake and wobble it by tiny amounts to look like a smooth motion. The larger the weight, the more you’ll see the wobbling action. Try making one out of the head of a scrub brush or small broom!

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Electrical Circuits & Components Exercises

Sunday March 7, 2010

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.

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Circuits & Components Exercises

1. LED stands for “Light Emitting Diode”. Does it matter which way you wire it up in a circuit? Does the longer wire on the LED connect to plus (red) or minus (black)?

2. Do you need to hook up batteries to make the neon lamp light up? What are 2 different ways you can make the neon lamp light up?

3. If you want to reverse the spin direction of a motor without using a switch, what can you do?

4. A simple switch can be made out of what kinds of materials?

5. Name six materials that are electrically conductive.

6. What’s the difference between a light bulb and your LED?

7. What happens when you rub your head with an inflated balloon? Which charge is where?

8. Why do electrical charges move in a circuit?

9. What makes lightning?

10. What’s the charge of an electron?

11. What happens when you split an electron open?

Need answers?

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Robotics Exercises

Sunday March 7, 2010

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1. Draw how you can connect a buzzer, LED, battery pack, and motor together AND have them all work at the same time.

2. How can you make a motor (that’s already wired up in your circuit) go faster?

3. What does a DPDT switch do? Draw six dots (like the six on a die) – these are the six terminals on your DPDT switch. Using your diagram, draw how you would connect the DPDT switch so that it can turn the motor on and off, as well as reversing it.

4. Can you use the same electrical circuit for the underwater robot as the laser light show? Why/why not?

5. Why does the pressure sensor work?

6. What kind of switch is the trip wire?

7. Name three ways you would improve the Jigglebot Robot.

Need answers?

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Answers to Robotics Exercises

Sunday March 7, 2010

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!

Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.

Answers:
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1. Connect the LED, motor, and buzzer in parallel (plus to plus) and they should all work.

2. Add a second battery pack to your circuit.

3. A DPDT switch allows you to reverse the motor direction by reversing the flow of electrons.

4. Yes – they both use the same circuit, including the motor speed control circuitry. They both need to control the speed and direction of the motors, and the electrical circuit doesn’t care whether you have a mirror or propeller on your motor shaft.

5. The sponge separates the foil, breaking the circuit open. When you squish the foam, the foil pieces touch and your light bulb lights up.

6. The trip wire is a NC (normally closed) switch.

7. I’d add headlights (LEDs), horn (buzzer), and wired remote control. How about you?

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Answers to Electricity Exercises

Sunday March 7, 2010

Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.

Answers:
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1. Yes, the longer lead is positive, and the side of the LED plastic housing that has a straight edge is negative.

2. No batteries required. The neon lamp requires very little amps, but high voltage to illuminate, which you can get by charging yourself up. Simply hold one lead and scuff along the carpet and touch the other lead to your cat’s nose. Or hold one lead and slide down a non-metal slide. Poof!

3. Switch the wires on the back of the motor at the terminals.

4. Take the two wires (one from the battery and the other from the motor) and touch them together – ON – OFF – ON – OFF. Simplest switch in the world! But you can also use index cards, paper clips, and brass fasteners. Clothespins work great, too.

5. Soda cans, quarters, paper clips, braces, unpainted eyeglasses, and your tongue.

6. A light bulb works both ways when you connect it into a circuit, an LED is polarized (only works one way).

7. Blow up a balloon. If you rub a balloon on your head, the balloon is now filled up with extra electrons, and now has a negative charge. The balloon is negatively charged.

8. There’s an imbalance of charges when you hook up a battery, causing the electrons to zip around the circuit.

9. There’s an imbalance of charge when lightning strikes. It’s the same thing a when you scuffed along the carpet, gathering up electrons in your body, only the lightning has a lot more charge.

10. Negative.

11. Nothing – an electron is as small as you can get. At least, as far as we know now.

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Basic Circuits

Sunday March 7, 2010

An electrical circuit is like a raceway or running track at school. The electrons (racecars) zip around the race loop (wire circuit) superfast to make stuff happen. Although you can’t see the electrons zipping around the circuit, you can see the effects: lighting up LEDs, sounding buzzers, clicking relays, etc.

There are many different electrical components that make the electrons react in different ways, such as resistors (limit current), capacitors (collect a charge), transistors (gate for electrons), relays (electricity itself activates a switch), diodes (one-way street for electrons), solenoids (electrical magnet), switches (stoplight for electrons), and more. We’re going to use a combination diode-light-bulb (LED), buzzers, and motors in our circuits right now.

A CIRCUIT looks like a CIRCLE. When you connect the batteries to the LED with wire and make a circle, the LED lights up. If you break open the circle, electricity (current) doesn’t flow and the LED turns dark.

LED stands for “Light Emitting Diode”. Diodes are one-way streets for electricity – they allow electrons to flow one way but not the other.

Remember when you scuffed along the carpet? You gathered up an electric charge in your body. That charge was static until you zapped someone else. The movement of electric charge is called electric current, and is measured in amperes (A). When electric current passes through a material, it does it by electrical conduction. There are different kinds of conduction, such as metallic conduction, where electrons flow through a conductor (like metal) and electrolysis, where charged atoms (called ions) flow through liquids.

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Here's what you need:

2 AA heavy duty (carbon) batteries - Do not use alkaline or rechargeable batteries
AA battery case
2 alligator wires
LEDs (any you choose is fine)

Download Student Worksheet & Exercises

Be alert for:

1. Batteries inserted into the case the wrong way!

2. LED in the wrong way (LEDs are picky about plus and minus - they are POLARIZED)

3. Is there a metal-to-metal connection? (You're not grabbing ahold of the plastic insulation, are you?)

4. Bad wires can cause headaches - if all else fails, then swap out your alligator clip lead wires for new ones.

Exercises

What does LED stand for?
Does it matter which way you wire an LED in a circuit?
Does the longer wire on the LED connect to plus (red) or minus (black)?
Do you need to hook up batteries to make a neon bulb light up? Why or why not?
What's the difference between a light bulb and your LED?
What is the difference between a bolt of lightning and the electricity in your circuit?
What is the charge of an electron?

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Waterbots

Sunday March 7, 2010

ROV stands for Remotely Operated Vehicle. These robots are used by scientists to explore the waters both offshore and in the deep sea, and often bring back samples and/or take video of their underwater findings. ROVs usually have a tether from the vehicle to the boat, which lightens up the load quite a bit (as it no longer needs to carry its own power or data storage). Powerful motors, such as bilge pumps or 24VDC motors, enable this robot to move in all six directions. ROVs are designed to be slightly positive in buoyancy, so they can surface automatically during power failures.

Of the robots we’re going to build, waterbots have the highest instant-success rate. You basically attach a motor to a piece of foam, stick it in the water, and it either floats and zips around, or capsizes and acts like an odd submarine. Either way, kids shriek with delight that their creation actually moves.

We’re going to use foam to create a waterbot, which will be powered by a simple electrical circuit. The hardest part of this activity will actually be building it stable enough so it doesn’t capsize. Boats are always built in a way so they don’t get pushed or flipped over easily by carrying a ballast, or extra weight, at the lowest part of the boat. You’ll need to figure out where to out your motor and batteries (which weigh a lot compared to a foam block) in order to balance your boat.

One of the biggest hurdles to overcome when building junkyard robots is friction. Since the motors have high speed and low torque, they can be difficult to use without a gearbox (which is both hard to find and out of the scope of this class). Since water has little friction, the robot will move about quite easily in the wet environment. We offer kids waterproof materials to build their robots with so that in the event their invention has trouble moving, we usually toss it in the pool to see if it can swim… which sparks another avenue of creativity and another round of improvements. Just be sure to keep the batteries out of the water. Are you ready?

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Materials:

1 propeller (read comments for ideas on where to find one)
foam block (this can be a scrap piece from packing material)
3VDC motor
AA battery case with AA batteries
2 alligator clip lead wires
hot glue gun with glue sticks

When you stick a block of wood in the water, it floats. If you make a small bowl out of tinfoil and place it in the water, it will also float. But if you crumple up the foil into a ball, it sinks. Certain materials like ice, wood, and foam blocks float no matter what shape they are. Some materials use their shape to decide whether they sink or float. A block of steel will usually sink unless you shape it into a boat (think about gigantic oceanliners!) Clay works the same way, as do many materials. So why is that?

Let’s take a look at our steel example. Steel is more dense than water. One pound of water takes up more space than one pound of steel, so it sinks when you place it in water. When you shape the steel into a boat, the steel fills with air. Steel and air together are less dense than water, so your oceanliner floats.

Hot tips for wet robots: You won’t get shocked by placing the batteries in the water – the amperage is too low. The motors are completely safe to submerge in the water, but they won’t last more than a few weeks from this treatment so stock up on a few extra. You can waterproof the motors (seal holes on motor with electrical tape, insert into a tight-fitting canister with a snap-on lid, seal with silicone, punch hole in lid, solder wires to terminals, let dry, snap on lid), but it’s often more trouble than it’s worth.

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Jigglebots

Sunday March 7, 2010

Ever wonder how a cell phone vibrates? What mechanism could be in such a tiny space to make the entire phone jiggle around? Well, there’s a tiny motor inside with an off-center weight on the shaft, called an eccentric drive.

You can still see eccentric drive mechanisms in older steam engines where the rotational motion is converted to liner? movement. Eccentrics are also found on tandem bicycles with timing chains.

Kids can make this robot in less than five minutes, but it will take hours to get all their modifications and adjustments just right. This robot works by wobbling, and the sloppier the kids are in their construction, the better the robot dances around. Play with the placement of the weight (battery pack) and the legs. Add more skewers, adjust their position and angle until you get it dancing without toppling over.

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Materials:

10 (or more) skewers
foam block
3VDC motor
wooden clothespin
AA battery case with AA batteries
2 alligator clip lead wires
hot glue gun with glue sticks
Optional: gear that fits onto the motor (you can alternately drill a hole in the clothespin as shown in the video)

Start building your dancing jigglebot by watching this video:

Most kids will make the legs parallel to the vertical, but quickly find that having the skewers flared out makes for a more stable design. Some jigglebots will spin in circles, others just stand and shake, and still others will zip off at a good pace in a straight line. We use a clothespin so you can add more weight (clip something inside the clothespin) if you need to.

Tip: The ‘sloppier’ kids build this robot, the better it moves. Enjoy!

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Conductivity Testers

Sunday March 7, 2010

Make yourself a grab bag of fun things to test: copper pieces (nails or pipe pieces), zinc washers, pipe cleaners, Mylar, aluminum foil, pennies, nickels, keys, film canisters, paper clips, load stones (magnetic rock), other rocks, and just about anything else in the back of your desk drawer.

Certain materials conduct electricity better than others. Silver, for example, is one of the best electrical conductors on the planet, followed closely by copper and gold. Most scientists use gold contacts because, unlike silver and copper, gold does not tarnish (oxidize) as easily. Gold is a soft metal and wears away much more easily than others, but since most circuits are built for the short term (less than 50 years of use), the loss of material is unnoticeable.
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Modify your basic LED circuit into a Conductivity Circuit by removing one clip lead from the battery and inserting a third clip lead to the battery terminal. The two free ends are your new clips to put things in from the grab bag. Try zippers, metal buttons, barrettes, water from a fountain, the fountain itself, bike racks, locks, doorknobs, unpainted benches… you get the idea!

Here’s what you need:

2 AA batteries
AA battery case
3 alligator wires
LEDs (any you choose is fine)
paper clip
penny
other metal objects around your house (zippers, chairs, etc…)

Why does metal conduct electricity?

Why does metal, not plastic, conduct electricity? Imagine you have a garden hose with water flowing through it. The hose is like the metal wire, and the water is like the electric current. Trying to run electricity through plastic is like filling your hose with cement. It’s just the nature of the material.

Download Student Worksheet & Exercises

Exercises

Name six materials that are electrically conductive.
What kinds of materials are conductors and insulators?
Can you convert an insulator into a conductor? How?
Name four instances when insulators are a bad idea to have around.
When are insulators essential to have?

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Simple Switches

Sunday March 7, 2010

When you turn on a switch, it’s difficult to really see what’s going on… which is why we make our own from paperclips, brass fasteners, and index cards.

Kids can see the circuit on both sides of the card, so it makes sense why it works (especially after doing ‘Conductivity Testers’).

SPST stands for Single Pole, Single Throw, which means that the switch turns on only one circuit at a time. This is a great switch for one of the robots we’ll be making soon, as it only needs one motor to turn on and off.
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Think of this switch like a train track. When you throw the switches one way, the train (electrons) can race around the track at top speed. When you turn the switch to the OFF position, it’s like a bridge collapse for the train – there’s no way for the electrons to jump across from the brass fastener to the paper clip. When you switch it to the ON position (both sides), you’ve rebuilt the bridges for the train (electrons).

Troubleshooting: The two tabs on the back of the motor are the places to clip in the power from the battery pack. Since these motors spin quickly and the shaft is tiny, add a piece of tape to the shaft to see the spinning action more clearly.

Kids can make their own switches so they can trace the path the electricity takes with a finger. See what you think about this SPST:

Here’s what you need:

2 AA batteries
AA battery case
3 alligator wires
index card
2 brass fasteners
paper clips
buzzer, motor, or LED

Download Student Worksheet & Exercises

Exercises

If you want to reverse the spin direction of a motor without using a switch, what can you do?
A simple switch can be made out of what kinds of materials?
How would you make your SPST switch an NC (normally closed) switch?
How did you have to connect your circuit in order for both the LED and motor to work at the same time? Draw it here:
Draw a picture of your experiment that explains how the SPST switch works, and show how electricity flows through your circuit:

Extra Credit (for students who have completed Part 3):

Draw a picture of your experiment that explains how the DPDT switch works in your circuit and show how to wire up the circuit.

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How to use a Digital MultiMeter

Sunday March 7, 2010

meter One of the most useful tools a scientist can have! A digital multimeter can quickly help you discover where the trouble is in your electrical circuits and eliminate the hassle of guesswork. When you have the right tool for the job, it makes your work a lot easier (think of trying to hammer nails with your shoe).

We'll show you how to get the most out of this versatile tool that we're sure you're going to use all the way through college. This project is for advanced students.

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Download Student Worksheet & Exercises

Exercises

If you measure 2.65 volts from your battery pack, do you need new batteries or will they work?
How do you think you would measure the resistance of an LED?
Reset your meter for a quick practical test: Remove the wires from your DMM and set the dial at OFF. Wave your hand wildly and show how you can use the meter (you can add probes and turn it on now) to test the voltage on your LED in a simple circuit doing the steps from the experiment.

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BumperBot

Sunday March 7, 2010

If you have a pet, they’ll be sure to get a great workout chasing this nifty little robot. If you can, I totally encourage you to make two or more and have a contest!

This BumperBot is one of the simplest robots you can make that uses a touch sensor, tricycle gear, and simple parts from around the house. (And there’s no computer programming required.) Using a switch that reverses direction upon impact, this robot will have your kid’s mind-wheels spinning. Be sure to follow the wiring directions EXACTLY as shown or it won’t work right!

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Here’s what you need:

four fat popsicle sticks
two pennies
1.5-3VDC hobby motor
two AA battery cases with AA batteries
alligator clip wires
2 wooden skewers
2 straws
three wheels or lids from film canisters, or milk jug lids (anything plastic, round, and about the size of a quarter)
scissors
hot glue gun and glue sticks

See if you can improve our design after you’ve built one. Here’s what you do:

Okay, so – here’s the deal: we’re going to make a home-brew slide switch that will reverse the direction of the motor when pressed. You can add additional circuits to sound a buzzer or blink on the headlights when the motors reverse, too!

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Race Cars

Sunday March 7, 2010

Racerbots can steer, unlike the Jigglebot. If you have more than one motor on your robot frame, you can turn either left, right, or spin on command. Wired remote control instructions follow this project.

These racerbots are the toughest of these robots to build. The wheels need to be squarely set on their shafts, all wheels need to be parallel, long wires out of the way, the motors spinning in the right direction, the battery pack in the right position… does this sound like a headache yet? Pay attention to construction details in the video and you’ll have less to fix later on.

Construction Tip: Cut the dowels in half to use for the axles and use the milk jug lids or film canister tops for wheels (you can also rip small, lightweight wheels off an old toy if they are about the size of a quarter). You may need to sand the dowels slightly if they are hard to fit into the wheels.

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Materials:

4 popsicle sticks
1 straw
4 wheels or lids from film canisters, or milk jug lids (anything plastic, round, and about the size of a quarter)
1 skewer
Two 3VDC motors
AA battery case with AA batteries
2 alligator clip lead wires
hot glue gun with glue sticks

Troubleshooting: To increase your motor speed, you’ll need to add a second battery pack. If you find the back wheels are slipping, run a bead of hot glue around the circumference of each wheel and carefully lay the flat side of a cut rubber band around the wheel (trim excess).

If the wheels spin in the opposite direction, your car will spin donuts (which could be fun!). If the car doesn’t move at all, use the basic circuit troubleshooting tips covered in previous experiments. (Are the batteries in the right way? Metal-to-metal connection? Fresh batteries? New wires?) Check to see if all four wheels spin freely without power. Roll the car down a ramp – does it travel relatively straight? If your robot keeps tripping over its wires, wrap the long lengths around the popsicle sticks or use shorter wires (cut in half, strip the insulation off, twist the exposed metal end on your electrical connections, and secure with tape).

What’s the next step? The instructions here are just for the chassis and propulsion systems of your robots. We’ll help you with the body framework and getting the robot to move. It’s up to you to add eyeballs, tentacles, claws, or whatever else you want to this framework.

You can click here to learn how to make the remote control for the waterbot and the racecar soap box remote controls. Have fun!

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Wiring Up Motors

Sunday March 7, 2010

Imagine you have two magnets. Glue one magnet on an imaginary record player (or a ‘lazy susan’ turntable) and hold the other magnet in your hand. What happens when you bring your hand close to the turntable magnet and bring the north sides together?

The magnet should repel and move, and since it’s on a turntable, it will circle out of the way. Now flip your hand over so you have the south facing the turntable. Notice how the turntable magnet is attracted to yours and rotates toward your hand. Just as it reaches your hand, flip it again to reveal the north side. Now the glued turntable magnet pushes away into another circle as you flip your magnet over again to attract it back to you. Imagine if you could time this well enough to get the turntable magnet to make a complete circle over and over again… that’s how a motor works!

After you get the buzzer and the light or LED to work, try spinning a DC motor:

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Here’s what you need:

2 AA batteries
AA battery case
2 alligator wires
1.5-3V DC motor
optional: propeller

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Superfast Bug Bot

Sunday March 7, 2010

This project is advanced students. If you like tiny robots, then this one is for you! Powered by cheap hobby motors, this fast little robot zips ’round and avoids obstacles using momentary switches and an idler wheel for a tail.

I recommend watching the entire video first, then rewind and watch again, this time building as you go. Make sure you have all your parts laid out ahead of time, or you’ll get frustrated partway through if you have to stop. You will need a soldering iron to make this project.

Here’s what you do:
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You will need to find:

1 large paper clip
1 round bead that fits onto the large paperclip
2 small paperclips
Insulated wire (you can also use the wire from your battery holder, as you’ll have to snip most of it off anyway)
Soda can (empty and clean)
AA battery holder with AA batteries
2 momentary switches
2 3-VDC motors (with gear attached if you can find them)
2 3/16″ female “quick disconnect” connectors
Heat shrink tubing or electrical tape
Optional: slide switch

Tools:

Wire strippers
Pliers
Soldering iron, solder, stand

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Underwater R.O.V. Robot

Sunday March 7, 2010

This project is for advanced students.

Up until 200 years ago, people thought the oceans were bottomless. The diving bell was one of the first recorded attempts at undersea exploration, and was simply a five-foot inverted cup with viewing holes on a platform that lowered into the water, which allowed people to breathe the trapped air inside… until they ran out of air. Leonardo da Vinci draw several sketches of underwater submersibles, and in the 1700s, John Lethbridge invented a long wooden cylinder with glass ends as one of the first diving units to reach 60 feet.

In 1930, two explorers used the bathysphere (a giant ball with windows) reached 1,428 feet below the surface, which was later followed by the bathyscape (deep diving vessel) that reached the deepest part of the Pacific Ocean, the Marianas Trench, at 35,800 feet in 1960.

The ROVs first made their appearance in the late 1960s, when military and offshore drilling required deeper dives. In the late 1980s, scientists needed a way to explore the remains of the Titanic, and a lower-cost, lighter weight version design was developed. ROVs are designed to be remote extensions of the operator.

One of the biggest challenges with deep-diving underwater vessels is keeping the tremendous pressure from crumpling the frame. The project we’re going to design is meant for swimming pools and smaller lakes. When designing your underwater vehicle, you’ll need to pay close attention to the finer details such as waterproofing the electrical motors and maintaining proper balance so that your robot doesn’t flip over or swim in circles.

Learn about thruster motors, create the chassis, and build the controller for these super-popular underwater robots that really swim in water! A fantastic project for parents and kids to work together on. Your underwater robot will move in all six directions and utilizes a 12V power source.

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You are about to embark on the adventure of creating and operating your own ROV underwater robot. As with all Supercharged Science educational items, we want kids to discover that science isn’t in the special parts that come with a kit, but rather in the imagination and skill of the kid building it. We strive to avoid parts that are specially made just for a kit, molded plastic pieces, etc. and instead use parts that any kid could buy from the store. This means that kids can feel free to change things around, use their own ideas to add improvements and whatever else their imagination can come up with. So on this note, let’s get started.

WARNING: This project is intended for kids over age 12, and requires adult supervision. Here are things to keep in mind:

The soldering iron reaches temperatures over 750^○F. It can obviously cause severe burns and serious injury. Always put it in the stand when not in use. Don’t look away while using it. Unplug it as soon as you’re done and set it in a place to cool where it won’t get knocked over.
Solder sometimes contains lead. Just don’t get it near your face and wash your hands when you’re done touching it. Plus, the usual warning that lead causes disease, it’s toxic, don’t feet it to you pets and keep it away from children.
The thruster motors in this kit are VERY powerful. The propellers (when turning) will easily cut through skin and flesh if you touch them! (Don’t be fooled because they’re plastic). NEVER touch them with anything when they are turning. Treat them like you would a power saw. Always disconnect power before working on them (short circuits can make them start unexpectedly).
PLEASE use common sense. Think like a real scientist: If something seems like it might be dangerous, it probably is. The real world doesn’t have warnings on everything that could possibly hurt you. I ask that you apply similar good judgment in using this kit. If you’re not sure, ASK for help. Ask a parent. And parents, if you need help, email or call us.
Okay, I’m required to say this one: This kit contains small parts, plastic bags and other choking hazards. Children under 3 years of age should not be allowed to touch it. (Obviously this is true since it’s meant for kids over 12.)

Omit the 2″ float pieces and instead put a pool noodle around the 1/2″ PVC, and also skip the toilet seal wax for sealing the thrusters (not sure if the video has this step or if we omitted it already) and just use straight hot glue. The frame does not need to be airtight, so if you’re concerned about fumes, just use hot glue for the entire project. — UPDATED ROV DESIGN: Omit the 2″ float pieces and instead put a pool noodle secured with zip ties around the 1/2″ PVC, and seal each thruster with hot glue. The frame does not need to be airtight, so if you’re concerned about fumes from the PVC glue, just use hot glue for the entire project.

Materials:

The parts you’ll need are as follows:

Glue & Fasteners

Superglue (0.5 oz. bottle or more)
Hot glue gun and extra glue sticks
Tube of silicone sealant or caulking
Petroleum jelly (Vaseline)
6 pcs. #6 x ½” stainless steel or brass sheet metal screws
6 pc. #6 stainless steel washers
10 pcs. 6” x 3/16” zip ties
Old newspapers to work on
Paper towels to clean up with

Frame Parts

5 ft. of ½” schedule 40 PVC pipe (Have it cut into these pieces at the store)
- 6 pcs. 1.5″ long
- 8 pcs. 4″ long
- 2 pcs. 6.5″ long
10 pcs. ½” schedule 40 PVC 90-degree elbows
4 pcs. ½” schedule 40 PVC tee’s
2 ft. of 2” schedule 40 PVC pipe (Have it cut into two 6″ pieces at the store)
4 pcs. 2” schedule 40 PVC end caps
3 thruster housings (plastic vials like film canisters… something that the hobby motors can fit into snugly)
3 pieces of 1” metal semicircular conduit straps (w/2 screw holes. 1” conduit)
10” x 6.5” piece of plastic hardware cloth (1/4” squares) – it looks like a plastic mesh grid. If you have chicken wire on hand, then you can use that instead.

Electrical parts

Three 12V DC motors
3 thruster propellers (drill out with 3/32” holes) – boat propellers from a hobby store work great
3 DPDT center-off screw terminal switches
Electrical tape (good quality) OR 2 pcs. #31 wire nut connectors
30 ft. of “CAT-3” (or “CAT-5”) telephone/network cable (8-conductor or 4-pair, AWG 24)
Rectangular project box (Approx. 4” x 6” x 3”)
12V Battery (two 6-volt lantern batteries, an old motorcycle or car battery or an “automotive jump starter” rechargeable power source)

Tools

Wire strippers
Long nose pliers
Soldering iron & stand with solder
An electric drill
Assorted drill bits (Specifically: 3/32”, 1/8”, 1/4”)
Razor knife
Hack saw or PVC pipe cutter
Flathead screwdrivers
Scissors
#120 sandpaper
A ruler or measuring tape

Okay, so you’re ready to go. Oh, a couple of notes. First, if your thruster housings are not snug enough in the pipe clamps, just wrap electrical tape around them a few times to add a little bit of extra thickness. One other thing. You may choose to solder alligator clips to your battery wires to make them easier to connect. Just clip the alligator clip on something large to open its jaws, slip off the rubber part and solder your wire on.

Happy Exploring!

Learn how to turn this project into a winning Science Fair Project!
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Pressure Sensor Burglar Alarm

Sunday March 7, 2010

However, if you walked around on stilts indeed of feet, and the ‘footprint’ of each stilt averaged 1” on each side, you’d now exert 100 psi per foot. Why such a difference?

So how do we use pressure in this experiment? When you squeeze the foam, the light bulb lights up! It’s ideal for under a doormat or carpet rug where lots of weight will trigger it.

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Here’s what you need:

thin sponge or foam square (about 1″ square)
AA battery case
2 AA batteries
3 alligator clip wires
2 large paper clips
scissors
aluminum foil
buzzer or LED

Download Student Worksheet & Exercises

Exercises

How does this sensor work?
What makes this an NO switch?
How can you use both the trip wire and the pressure sensor in the same circuit? Draw it out here:

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Latching Circuit

Sunday March 7, 2010

Once you’ve made the Pressure Sensor burglar alarm, you might be wondering how to make the alarm stay on after it has been triggered, the way the Trip Wire Sensor does.

The reason this isn’t as simple as it seems is that the trip wire is a normally closed (NC) switch while the pressure sensor is a normally open (NO) switch. This means that the trip wire is designed to allow current to flow through the tacks when there’s no paper insulating them, while the pressure sensor stops current flowing in it’s un-squished state. It’s just the nature of the two different types of switches.

However, we can build a circuit using a relay which will ‘latch on’ when activated and remain on until you reset the system (by cutting off the power). This super-cool latching circuit video will show you everything you need to know.
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Materials:

relay (from Unit 11)
your completed Pressure Sensor circuit
SPST switch (optional)

Download Student Worksheet & Exercises

Use 9V for your batteries, the first switch is SPST, the second is the pressure sensor, the B stands for ‘buzzer’. The spring-looking thing is the relay coil, and the contacts are the three lines above the circuit hooked on either side of the second switch. Watch the video for real-time step-by-step instructions on how to build this!

Exercises

What is a relay?
What does the relay do in this circuit?
Draw out a picture that shows how everything is connected in your circuit:

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Trip Wire Burglar Alarm

Sunday March 7, 2010

Burglar alarms not only protect your stuff, they put the intruder into a panic while they attempt to disarm the triggered noisemaker. Our burglar alarms are basically switches which utilize the circuitry from Basic Circuits and clever tricks in conductivity.

A complete and exhaustive description of electronics would jump into the physics of solid state electronics, which is covered in undergraduate university courses. Instead, here is a quick description based on the fluid analogy for electric charge:

The movement of electric charge is called electric current, and is measured in amperes (A, or amps). When electric current passes through a material, it does so by electrical conduction, but there are different kinds of conduction, such as metallic conduction (where electrons flow through a conductor, like metal) and electrolysis (where charged atoms (called ions) flow through liquids).

Why does metal conduct electricity? Metals are conductors not because electricity passes through them, but because they contain electrons that can move. Think of the metal wire like a hose full of water. The water can move through the hose. An insulator would be like a hose full of cement – no charge can move through it.

[am4show have=’p8;p9;p20;p47;p108;’ guest_error=’Guest error message’ user_error=’User error message’ ]Paper doesn’t conduct electricity – it’s an insulator, just like plastic. The trip wire is an NC (normally closed) switch, meaning that this circuit works until you trigger the switch. So we need a way to stop the current (flow of electrons) until we want the buzzer to activate.

When you stick the paper index card between the two tacks in the clothespin, it breaks the electrical connection and the switch goes in the OFF position. Remove the paper and your switch moves to the ON position, and electrons are flowing around and around your circuit, and you hear a BUZZZZZZZZZ!

This alarm has a thin wire that someone “trips”, which pulls out the card, closes the switch, and sounds a buzzer or lights up an LED!

Here’s what you need:

AA battery case
2 AA batteries
3 alligator clip wires
wood clothespin
4-6″ piece of steel or (stripped) copper wire
2 tacks (or wrap jaws with aluminum foil)
buzzer or LED

Download Student Worksheet & Exercises

Troubleshooting: The trip wire is a NC (normally closed) switch. The buzzer makes noise until you ‘push’ (squeeze, really) the switch. To arm the trip wire, insert a small card between the tacks. The card works because paper does not conduct electricity. When the card gets yanked out, the tacks touch and… BUZZ!!!

Installation Tip: Hide this switch down low by the door frame and use fishing line instead of string to make this burglar alarm virtually invisible. Use a tack in the frame or tie the line to the door hinge to secure and wait for the action…

Exercises

How does this work?
What type of switch is the trip wire?
Name three places you can install this alarm.

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Dimmers and Motor Speed Controllers

Sunday March 7, 2010

So now you know how to hook up a motor, and even wire it up to a switch so that it goes in forward and reverse. But what if you want to change speeds? This nifty electrical component will help you do just that.

Once you understand how to use this potentiometer in a circuit, you’ll be able to control the speed of your laser light show motors as well as the motors and lights on your robots. Ready?

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Here’s what you need:

2 AA batteries
AA battery case
3 alligator wires
potentiometer
1.5-3V DC motor
LED (any you choose)

Download Student Worksheet & Exercises

Exercises

How does a potentiometer work?
Does the potentiometer work differently on the LED and the motor?
Name three places you’ve used potentiometers in everyday life.
How do you think you might wire up an LED, switch, and potentiometer?

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Forward and Reverse Motor Control

Sunday March 7, 2010

Once you’ve made a a simple switch, you’re ready to use more advanced electrical components, such as the DPDT switch you picked up from an electronics store (refer to shopping list for this section). When you wire up this nifty device, you’ll be able to get your motors to go forward, reverse, and stop… all with the flip of a switch.

You can use this component along with a potentiometer so you can not only control the direction but also the speed of a motor, like in a robot or laser light show. And don’t feel limited on using this switch just with motors – it works with bi-polar LEDs and other things as well. For example, you can hook this up so that when it’s in the UP position, the buzzer sounds, and the DOWN position makes the headlights go on. Are you ready to learn how to wire this one up?

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Click here to learn how to incorporate this switch into your robot by making a simple remote control.
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Salty Battery

Sunday March 7, 2010

Using ocean water (or make your own with salt and water), you can generate enough power to light up your LEDs, sound your buzzers, and turn a motor shaft. We’ll be testing out a number of different materials such as copper, aluminum, brass, iron, silver, zinc, and graphite to find out which works best for your solution.

This project builds on the fruit battery we made in Unit 8. This experiment is for advanced students.

The basic idea of electrochemistry is that charged atoms (ions) can be electrically directed from one place to the other. If we have a glass of water and dump in a handful of salt, the NaCl (salt) molecule dissociates into the ions Na+ and Cl-.

When we plunk in one positive electrode and one negative electrode and crank up the power, we find that opposites attract: Na+ zooms over to the negative electrode and Cl- zips over to the positive. The ions are attracted (directed) to the opposite electrode and there is current in the solution.

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Here’s what you need:

water
salt
vinegar (distilled white)
bleach IMPORTANT: WEAR GOGGLES!
glass container (like a cleaned out jam jar)
electrodes
real silverware (not stainless)
shiny nail (galvanized)
large paper clip
dull nail (iron)
wood screws (brass)
copper pennies minted before 1982 (or a short section of copper pipe)
graphite from inside a pencil (use a mechanical pencil refill)
2 alligator wires
digital multimeter

Download Student Worksheet & Exercises

Here’s what you do:

Fill a cup with water, adding a teaspoon of salt, a teaspoon of distilled white vinegar, and a few drops of bleach. NOTE: BE very careful with bleach! Cap it and store as soon as you’ve added it to the cup.
Find two of the following materials: copper*, aluminum*, brass, iron, silver, zinc, graphite (* indicates the ones that are easiest to start with – use a copper penny and a piece of aluminum foil). Attach an alligator clip lead to each one and dunk into your cup. Make sure these two metals DO NOT TOUCH in the solution.
You’ve just made a battery! Test it with your digital volt meter and make a note of the voltage reading. Connect the multimeter in series to read the current (remove a clip from the metal and clip it to one test probe, and attach the other test probe to the metal. Make sure you’re reading AMPS, not VOLTS when you note the reading for current).
Test out different combinations of materials and note which gives the highest voltage reading for you. Is it enough to light an LED? Buzzer? Motor? What if you made two of these and connected them in series? Three? Four?

Electrochemistry studies chemical reactions that generate a voltage and vice versa (when a voltage drives a chemical reaction), called oxidation and reduction (redox) reactions. When electrons are transferred between molecules, it’s a redox process.

Fruit batteries use electrolytes (solution containing free ions, like salt water or lemon juice) to generate a voltage. Think of electrolytes as a material that dissolves in water to make a solution that conducts electricity. Fruit batteries also need electrodes made of conductive material, like metal. Metals are conductors not because electricity passes through them, but because they contain electrons that can move. Think of the metal wire like a hose full of water. The water can move through the hose. An insulator would be like a hose full of cement – no charge can move through it.

You need two different metals in this experiment that are close, but not touching inside the solution. If the two metals are the same, the chemical reaction doesn’t start and no ions flow and no voltage is generated – nothing happens.

Exercises

Which combination gives the highest voltage?
What happens if you use two strips of the same material?
What would happen if we used non-metal strips?

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Seeing Electric Fields Using Your Spice Rack

Sunday March 7, 2010

Have you wrapped your mind around static electricity yet? You should understand by now how scuffing along a carpet in socks builds up electrons, which eventually jump off in a flurry known as a spark. And you also probably know a bit about magnets and how magnets have north and south poles AND a magnetic field (more on this later). Did you also know that electrical charges have an electrical field, just like magnets do?

It’s easy to visualize a magnetic field, because you’ve seen the iron filings line up from pole to pole. But did you know that you can do a similar experiment with electric fields?

Here’s what you need:

dried dill (spice)
vegetable or mineral oil
2 alligator wires
static electricity source (watch video first!)

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Download Student Worksheet & Exercises

Here’s what you do:

1. Fill a saucer with vegetable or mineral oil.
2. Sprinkle small seeds or spices on top, such as caraway, anise, or dill (this one works best).
3. Build up an electric charge by either rubbing a balloon on your head, rubbing a PVC pipe with a wool sweater or mittens, or your favorite way to build up to a spark.
4. Bring the charged object near the oil – what happened to the spices?
5. Does it matter which end of the balloon/pipe/etc you hold near the oil? What if you move it a bit near the dish?
6. Stir the dill into the oil. Bring a charged object near and watch the dill spring up to touch the rod.

Troubleshooting:
If your dill isn’t moving at all, your object may be too ‘dirty’ (e.g. have too much oil from your fingers) on it to hold a charge. Clean it with rubbing alcohol after you use soap and water, and you should see better results.

What’s going on?
The dill/caraway/anise are all shaped like rods, which move to line up in the field (which is why round particles like cinnamon and pepper don’t work as well). The dill has a balance of charges – both plus and minus – and when you bring a charged object close, the negative charges in the dill are attracted to the balloon but the positive charges are repelled, so one side of the dill becomes minus and the other plus. Since the dill is free to move in the liquid, it lines up in the electric field to indicate the charge direction.

If you move the balloon just right, the attractive electrical charge will pull the lightweight dill right up out of the oil and onto the balloon. Have fun!

Exercises

What happened when you brought a charged balloon near the dill?
What side of the dill was attracted to the balloon?
What happened when you brought two negative charges near the dill?
Were you able to make the dill come out of the liquid and onto the balloon without touching the oil?

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Silver Battery

Sunday March 7, 2010

Never polish your tarnished silver-plated silverware again! Instead, set up a ‘silverware carwash’ where you earn a nickel for every piece you clean. (Just don’t let grandma in on your little secret!)

We’ll be using chemistry and electricity together (electrochemistry) to make a battery that reverses the chemical reaction that puts tarnish on grandma’s good silver. It’s safe, simple, and just needs a grown-up to help with the stove.

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Here’s what you need:

stove (with adult help)
skillet
aluminum foil
water
baking soda
salt
real silverware (not stainless)

Download Student Worksheet & Exercises

You can safely dip it into a self-polishing solution:

In a saucepan lined with aluminum foil, heat a solution of 1 cup water, 1 teaspoon baking soda, and 1 teaspoon salt.
When your solution bubbles, place the tarnished silverware directly on the foil. (Try a piece that’s really tarnished to see the cleaning effects the best.)

What’s happening? This is a very simple battery, believe it or not! The foil is the negative charge, the silverware is the positive, and the water-salt-baking-soda solution is the electrolyte.

Your silver turns black because of the presence of sulfur in food. Here’s how the cleaning works: The tarnished fork (silver sulfide) combines with some of the chemicals in the water solution to break apart into sulfur (which gets deposited on the foil) and silver (which goes back onto the fork). Using electricity, you’ve just relocated the tarnish from the fork to the foil. Just rinse clean and wipe dry.

Toss the foil in the trash (or recycling) when you’re done, and the liquids go down the drain.

Exercises

Where is the electrolyte in this experiment?
Where does the black stuff that was originally on the silverware go?
Where’s the electricity in this experiment?
Where would you place your DMM probes to measure the generated voltage?

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Air Battery

Sunday March 7, 2010

It’s easy to use chemistry to generate electricity, once you understand the basics. With this experiment, you’ll use aluminum foil, salt, air, and a chemical from an aquarium to create an air battery. This experiment is for advanced students.

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The first thing you should do is dig out your digital multimeter. We’ll be using this to find out just how much voltage your battery cell generates (and this will also tell you how many of these batteries you need to make to power a LED or motor.)

Here’s what you need:

salt
bowl of water
activated charcoal (from an aquarium supply store)
aluminum foil
paper towel
2 alligator clip leads

Download Student Worksheet & Exercises

Here’s what you do:

1. Make a saturated salt solution (dissolve as much salt as you can into water in a bowl). It’s better to have an over-saturated solution (so you still see undissolved bits at the bottom).

2. Rip off a square of aluminum foil and set it on your table.

3. Soak a sheet of paper towel in your salt solution, then gently fold in half (without tearing!) and lay on top of the foil.

4. Sprinkle a 1/2″ thick layer of activated charcoal on the damp towel.

5. Lay one alligator clip lead on the carbon (make sure the metal is exposed) in the center of the layer so it makes good contact with the carbon. Clip a second clip lead to the bottom layer of foil. Note that the two clip leads should not touch! And be sure the top clip lead is completely surrounded by the charcoal and has no chance of touching the aluminum foil.

6. Fold your layers over in thirds. Clip the two leads sticking out to your digital multimeter and check the voltage. If it’s higher than 2.5V, then try attaching an LED or motor. If it’s less than 2.5 volts, you’ll need to make a second (or third) battery and hook them up together to generate enough power to light stuff up.

7. Squish the battery to make good contact between the carbon, salt, and foil. Your voltage should change when you do this.

8. Use your digital voltmeter to measure your voltage again. Make a second battery and hook the new one’s positive to the first one’s negative terminal. The two wires left are your leads to connect to the multimeter (or LED).

How does it work?

Most homemade batteries light up LEDs and a few flashlight bulbs, but dimly. It takes a lot more current to get a motor spinning. So what gives?

This ‘aluminum air battery’ uses a chemical reaction between the foil and air (well, specifically the oxygen in the air). The combination of oxygen and foil produces aluminum oxide and energy. If you build your battery well, you can see the energy in your turning motor shaft, but the oxide layer will be invisible to your eye. Your battery should last between 4 – 10 minutes, depending on how well you built it. You can get a larger amount of voltage by using larger wires (with more surface area contacting the charcoal). What do you have that would be a larger electrode for the battery?

The more salt you use, the better your air battery will work! (You’ll notice there’s a point, though, where no matter how much more salt you add, you can’t increase the voltage… due to the saturation point of the water. Have you tried changing the temperature of the water to increase the capacity?)

Exercises

How many air batteries does it take for your LED to light up?
Which electrode is positive? Which is negative? (Hint: Use the DMM to figure this out.)
What is the electrolyte in this experiment?
What could you use instead of an exposed alligator clip lead to make this battery last longer?

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Nerve Tester

Sunday March 7, 2010

Electrical circuits are used for all kinds of applications, from blenders to hair dryers to cars. And games! Here’s a quick and easy game using the principles of conductivity.

This experiment is a test of your nerves and skill to see if you can complete the roller coaster circuit and make it from one end to the other. You can opt to make a noisy version (more fun) or a silent version (for stealth). Are you ready?

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Here’s what you need:

AA battery case
2 AA batteries
3 alligator wires
buzzer or LED
wire coat hanger (sandpaper might be needed if yours is coated with enamel)
popsicle stick
vice grips
tape
wood block or foam block

Download Student Worksheet & Exercises

Here’s what you do:

Insert batteries into cases and connect a buzzer (or LED for a silent game) so that it works. Set aside as you make the next part.
Using a paper clip, form a loop and secure to a popsicle stick so that it looks like a bubble wand, with the ends poking out of the bottom of the tape. Bend the ends up so you can clip onto them with your alligator clips later. (You should have ¼ – ½” poking upwards).
Bend and twist an un-insulated coat hanger wire into spirals and dizzy roller-coaster shapes. When you’ve got right, make a small loop at each end. Insert one screw into each small loop and screw into wood base, about 10” apart (be sure to thread the bubble wand loop onto wire first!). Your roller coaster wire should stand up on its own.
Disconnect the clip lead wire from your positive battery terminal and clip it to the exposed paper clip end on your popsicle-stick bubble-wand. Wrap the exposed end of the positive terminal around one end of the coat hanger near the screw and seal with tape.
Can you travel the entire path without setting off the buzzer (or light)? (The photo above has both!) Where in your circuit can you add a switch to turn the game on and off?

Troubleshooting:
1. Make sure your coat hanger is really just a bare rod of metal. Sandpaper the entire length before using it in the project.

2. Make sure the batteries are fresh and inserted the right way.

3. Use a block of wood or foam for best results… they are both excellent insulators for the wire track.

4. Places where kids most often forget to hook up: (a) connect the wire to a bare spot on the track itself, near the base; (b) be sure your loop also has a wire connection.

Exercises

Can you travel the entire path without turning on the light?
Where in your circuit can you add a switch to turn the game on and off?

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Electrolytes

Sunday March 7, 2010

When an atom (like hydrogen) or molecule (like water) loses an electron (negative charge), it becomes an ion and takes on a positive charge. When an atom (or molecule) gains an electron, it becomes a negative ion. An electrolyte is any substance (like salt) that becomes a conductor of electricity when dissolved in a solvent (like water).

This type of conductor is called an ‘ionic conductor’ because once the salt is in the water, it helps along the flow of electrons from one clip lead terminal to the other so that there is a continuous flow of electricity.

This experiment is an extension of the Conductivity Tester experiment, only in this case we’re using water as a holder for different substances, like sugar and salt. You can use orange juice, lemon juice, vinegar, baking powder, baking soda, spices, cornstarch, flour, oil, soap, shampoo, and anything else you have around. Don’t forget to test out plain water for your ‘control’ in the experiment!

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Here’s what you need:

2 AA batteries
AA battery case
2 alligator clips
LED
water
salt
glass jar (like a clean jam jar)

Download Student Worksheet & Exercises

Exercises

Why does electricity flow through some solutions but not all of them?
What is a salt?
How are electrolytes used today in real life?
Which substance was your top conductor?
Which substance didn’t conduct anything at all?
What happens if you mix an electrolyte and non-electrolyte together?

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Advanced Static Electricity Experiments

Sunday March 7, 2010

You can use the idea that like charges repel (like two electrons) and opposites attract to move stuff around, stick to walls, float, spin, and roll. Make sure you do this experiment first.

I’ve got two different videos that use positive and negative charges to make things rotate, the first of which is more of a demonstration (unless you happen to have a 50,000 Volt electrostatic generator on hand), and the second is a homemade version on a smaller scale.

Did you know that you can make a motor turn using static electricity? Here’s how:

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Download Student Worksheet & Exercises

Here’s how the electrostatic machine works – you will need:

a yardstick
spoon
balloon

How does it work? Different parts of the atom have different electrical charges. The proton has a positive charge, the neutron has no charge (neutron, neutral get it?) and the electron has a negative charge. These charges repel and attract one another kind of like magnets repel or attract. Like charges repel (push away) one another and unlike charges attract one another.

So if two items that are both negatively charged get close to one another, the two items will try to get away from one another. If two items are both positively charged, they will try to get away from one another. If one item is positive and the other negative, they will try to come together.

How do things get charged? Generally things are neutrally charged. They aren’t very positive or negative. However, occasionally (or on purpose as we’ll see later) things can gain a charge. Things get charged when electrons move. Electrons are negatively charged particles. So if an object has more electrons than it usually does, that object would have a negative charge. If an object has less electrons than protons (positive charges), it would have a positive charge.

How do electrons move? It turns out that electrons can be kind of loosey-goosey. Depending on the type of atom they are a part of, they are quite willing to jump ship and go somewhere else. The way to get them to jump ship is to rub things together.

Remember, in static electricity, electrons are negatively charged and they can move from one object to another. This movement of electrons can create a positive charge (if something has too few electrons) or a negative charge (if something has too many electrons). It turns out that electrons will also move around inside an object without necessarily leaving the object. When this happens the object is said to have a temporary charge.

Try this: Blow up a balloon. When you rub the balloon on your head, the balloon is now filled up with extra electrons, and now has a negative charge. Now stick it to a wall— to create a temporary charge on a wall.

Opposite charges attract right? So, is the entire wall now an opposite charge from the balloon? No. In fact, the wall is not charged at all. It is neutral. So why did the balloon stick to it?

The balloon is negatively charged. It created a temporary positive charge when it got close to the wall. As the balloon gets closer to the wall, it repels the electrons in the wall. The negatively charged electrons in the wall are repelled from the negatively charged electrons in the balloon.

Since the electrons are repelled, what is left behind? Positive charges. The section of wall that has had its electrons repelled is now left positively charged. The negatively charged balloon will now “stick” to the positively charged wall. The wall is temporarily charged because once you move the balloon away, the electrons will go back to where they were and there will no longer be a charge on that part of the wall.

This is why plastic wrap, Styrofoam packing popcorn, and socks right out of the dryer stick to things. All those things have charges and can create temporary charges on things they get close to.

Want to purchase an electrostatic machine? Here’s a link to the one used in the video called a Wimshurst Machine which makes sparks up to 4″ long. For younger kids, we recommend this fun hand-held, non-shocking electrostatic generator.

Exercises

What happens if you rub the balloon on other things, like a wool sweater?
If you position other people with charged balloons around the table, how long can you keep the yardstick going
Can we see electrons?
How do you get rid of extra electrons?
Why do you think the yardstick moved?
What would happen if you use both a positively charged object and a negatively charged object to make the yardstick move?

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Alien Detector (Advanced)

Sunday March 7, 2010

This simple FET circuit is really an electronic version of the electroscope. This “Alien Detector” is a super-sensitive static charge detector made from a few electronics parts. I originally made a few of these and placed them in soap boxes and nailed the lids shut and asked kids how they worked. (I did place a on/off switch poking through the box along with the LED so they would have ‘some’ control over the experiment.)

This detector is so sensitive that you can go around your house and find pockets of static charge… even from your own footprints! This is an advanced project for advanced students.

You will need to get:

9V battery clip (and a 9V battery)
MPF 102 (buy 2 – one for back up)
LED (any regular LED works fine)

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Download Student Worksheet & Exercises

After you’ve made your charge detector, turn it on and comb your hair, holding the charge detector near your head and then the comb. You’ll notice that the comb makes the LED turn off, and your head (in certain spots) makes the LED go on. So it’s a positive charge static detector… this is important, because now you know when the LED is off, the space you’re detecting is negatively charged, and when it’s lit up, you’re in a pocket of positively charged particles. How far from the comb does your detector need to be to detect the charge? Does it matter how humid it is?

You can take your detector outdoors, away from any standing objects like trees, buildings, and people, and hold it high in the air. What does the LED look like? What happens when you lower the detector closer to the ground? Raise it back up again to get a second reading… did you find that the earth is negative, and the sky is more positive?

You can increase the antenna sensitivity by dangling an extra wire (like an alligator clip lead) to the end of the antenna. Because thunderstorms are moving electrical charges around (negative charges downwards and positive charges upwards), the earth is electrified negatively everywhere. During a thunderstorm, the friction caused by the moving water molecules is what causes lightning to strike! (But don’t test your ideas outside in the wide open while lightening is striking!)

Exercises

When the LED is on, what do you think it means?
Does the LED turning off detect anything?
Do aliens like humidity?
How does this alien detector really work?

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Remote Controls I

Sunday March 7, 2010

Radio control (RC) is a 100 year-old technology. RC requires both a transmitter and a receiver. The control box sends commands to the robot the same way you change channels on the TV with the remote.

The difference between RC (radio control) and IR (infrared control) is in the frequency of the signals. With the radio controller, the light waves that carry the command information are lower energy, lower frequency signals. The TV remote uses higher energy, higher frequency infrared signals called CIR (consumer infrared).

Both RC and CIR require circuit design at a college graduate level. However, wired remote controls are well within the reach of any young budding scientist.

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By simply removing both the battery pack and switch assembly from the robot, stuffing them in a box, and extending the wires from the box to the robot, you’ve got a wired remote control and a lightweight (and usually faster-moving) robot.

Simple remote controls are a great addition for both the waterbot and race cars. Once the kids build the robot and they’ve gotten over the initial “WOW!” factor, they’ll probably wonder how to turn it off so they can work on it further.

This is an excellent place for a question… “How are you going to turn the motor on and off easily?”

Use the simple SPST switch for these two robots and use 10’ long wires (flexible one-line (2-wire) telephone cable works well).

Materials:

your robot that you want to control (use any from this section)
index card
2 brass fasteners
1 paper clip
2 additional alligator clip lead wires
optional: plastic soap container
optional: drill with drill bits

Advanced Tip: When you've mastered this switch, you can substitute the DPDT switch in your robot - this is the switch we use in the underwater ROV robot experiment.

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Remote Controls II

Sunday March 7, 2010

If you've made the waterbot, you can use this wired remove to make the motor turn both forward and reverse. All you need is an extra set of wires (telephone cable with two wires in it work great, or else twist two long wires together... they can be as long as you want.) Enclose the whole thing in a plastic box (I like to use tupperware or a soap box) and drill three holes in the top for the brass fasteners and one in the side for the wire and you're all set!

Materials:

your robot that you want to control (use any from this section)
index card
3 brass fasteners
1 paper clip
4 additional alligator clip lead wires
optional: plastic soap container
optional: drill with drill bits

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More Sensors

Sunday March 7, 2010

If you want your robot to detect when it’s flipped sideways, this is the sensor you need. It’s ridiculously simple to make, and works great as long as the metal makes good contact. I’ve also included instructions for making a motion sensor as well, just in case you need to detect motion or acceleration.

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Materials for the Tilt Sensor:

film canister
2 AA batteries
AA battery case
aluminum foil
buzzer or LED
alligator clip wires
small paper clips
scissors

Materials for the Motion Sensor:

wire coat hanger (sandpaper might be needed if your coat hanger is coated with enamel)
ball chain
film canister
vice grips
2 AA batteries
AA case
alligator clip wires
LED
scissors
tape

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Unit 10: Electricity (Robotics) Video

Sunday March 7, 2010

Now that you’ve got a good handle on circuits and electrical components, it’s time to pull it together into something useful, like building robots and sensors. Are you ready? Then let’s put your new ideas and electrical circuit building skills to the test…

Unit 10: Electricity (Circuits & Components) Video

Sunday March 7, 2010

Why study electricity? While it’s true that you don’t need to know how electricity works in order to flip on a light switch, but you do need to know a thing or two about circuits before you start wiring up your own robot. Electricity is all around you from the tiny subatomic level of the electron to the gigantic solar storms from the sun. When you’re done with this lesson, you’ll know how to wire up circuits for underwater vehicles, create your own robotics sensors, extract energy from fruit, split a water molecule, and really make sparks fly. Are you ready? This video will get you started on the right foot for your study into electricity:
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Electrical Safety – Best Batteries to Use

Wednesday February 3, 2010

Before you reach for the pack of Duracells, watch our video on the best batteries to use when starting out with your electricity experiments. (The answer is much cheaper than you think.) Here’s what you need to know:

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Fruit Battery

Sunday January 10, 2010

This experiment shows how a battery works using electrochemistry. The copper electrons are chemically reacting with the lemon juice, which is a weak acid, to form copper ions (cathode, or positive electrode) and bubbles of hydrogen.

These copper ions interact with the zinc electrode (negative electrode, or anode) to form zinc ions. The difference in electrical charge (potential) on these two plates causes a voltage.

Materials:

one zinc and copper strip
two alligator wires
digital multimeter
one fresh large lemon or other fruit

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Download Student Worksheet & Exercises

Roll and squish the lemon around in your hand so you break up the membranes inside, without breaking the skin or leaking any juice. If you’re using non-membrane foods, such as an apple or potato, you are all ready to go.

Insert the copper and zinc strips into the lemon, making sure they do not contact each other inside. Clip one test wire to each metal strip using alligator wires to connect to the digital multimeter. Read and record your results.

What happens when you gently squeeze the lemon? Does the voltage vary over time?

You can try potatoes, apples, or any other fruit or vegetable containing acid or other electrolytes. You can use a galvanized nail and a copper penny (preferably minted before 1982) for additional electrodes.

If you want to light a light bulb, try using a low-voltage LED in the 1.7V or lower hooked up to several lemons connected in series. For comparison, you’ll need about 557 lemons to light a standard flashlight bulb.

What’s going on?

Exercises

What kinds of fruit make the best batteries?
What happens if you put one electrode in one fruit and one electrode in another?
What happens if you stick multiple electrode pairs around a piece of fruit, and connect them in series (zinc to copper to zinc to copper to zinc…etc.) and measure the voltage at the start and end electrodes?

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Electroplating

Sunday January 10, 2010

If you don’t have equipment lying around for this experiment, wait until you complete Unit 10 (Electricity) and then come back to complete this experiment. It’s definitely worth it!

Electroplating was first figured out by Michael Faraday. The copper dissolves and shoots over to the key and gets stuck as a thin layer onto the metal key. During this process, hydrogen bubbles up and is released as a gas. People use this technique to add material to undersized parts, for place a protective layer of material on objects, to add aesthetic qualities to an object.

Materials:

one shiny metal key
2 alligator clips
9V battery clip
copper sulfate (MSDS)
one copper strip or shiny copper penny
one empty pickle jar
9V battery

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Download Student Worksheet & Exercises

Place the copper sulfate in your jar and add a thin stream of water as you stir. Add enough water to make a saturated solution (dissolves most of the solids). Connect one alligator wire to the copper strip and the positive (red) wire from the clip lead. Connect the other alligator wire to the key and the negative (black) lead.

Place the copper strip and the key in the solution without touching each other. (If they touch, you’ll short your circuit and blow up your battery.) Let this sit for a few minutes… and notice what happens.

Clean up: Clean everything thoroughly after you are finished with the lab. After cleaning with soap and water, rinse thoroughly. Chemists use the rule of “three” in cleaning glassware and tools. Rinse three times, wash with soap, rinse three times.

Wipe off the electrodes. The solution and solids at the bottom of your cup cannot go in the trash. The liquid contains copper, a toxic heavy metal that needs proper disposal and safety precautions. Another chemical reaction needs to be performed to remove the heavy metal from the copper sulfate: Add a thumb sized piece of steel wool to the solution. The chemical reaction will pull out the copper out of the solution. The liquid can be washed down the drain. The solids cannot be washed down the drain, but they can be put in the trash. Use a little water to rinse the container free of the solids.

Place all chemicals, cleaned tools, and glassware in their respective storage places.

Dispose of all solid waste in the garbage. Liquids can be washed down the drain with running water. Let the water run awhile to ensure that they have been diluted and sent downstream.

Exercises

Look at your key. What color is it?
Where did the copper on your key come from?
What happened when you added a second battery?
Which circuit (series or parallel) did the reaction accelerate faster with?

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Ten Static Electricity Experiments to Mystify Your Kids

Saturday March 7, 2009

The smallest thing around is the atom, which has three main parts – the core (nucleus) houses the protons and neutrons, and the electron zips around in a cloud around the nucleus.

The proton has a positive charge, and the electron has a negative charge. In the hydrogen atom, which has one proton and one electron, the charges are balanced. If you steal the electron, you now have an unbalanced, positively charge atom and stuff really starts to happen. The flow of electrons is called electricity. We’re going to move electrons around and have them stick, not flow, so we call this ‘static electricity’.

These next experiments rely heavily on the idea that like charges repel and opposites attract. Your kids need to remember that these activities are all influenced by electrons, which are very small, easy to move around, and are invisible to the eye.
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Blow up a balloon. If you rub a balloon on your head, the balloon steals the electrons from your head, and now has a negative charge. Your head now has a positive charge because your head was electrically balanced (same number of positive and negative charges) until the balloon stole your negative electrons, leaving you with an unbalanced positive charge.

Let’ play with a more static electricity experiments, including making things move, roll, spin, chime, light up, wiggle and more using static electricity!

Here’s what you need:

7-9″ balloon (get two in case one pops)
a wall
wool sweater or scarf
sink
ping pong ball
comb
neon bulb
tissue paper
wire coat hanger
tape
packing peanuts
bubble juice
fluorescent bulb (burnt-out bulbs are fine to use)
nylon stocking (AKA ‘panty-hose’)
plastic grocery bag

Download Student Worksheet & Exercises

Static Electricity Experiments!

Expt. 1: Static Hairdo Charge a balloon by rubbing it on your head for 30 seconds. Pull the balloon up about six inches to check your progress – if the hair isn’t sticking to the balloon, try again on someone with clean, dry hair (without any hair styling goop). When you put the balloon close to your head, notice how your hair reaches out for the balloon. Your hair is positive, the balloon is negative, and you can see how they are attracted to each other!
Your hair stands up when you rub it with a balloon because your head is now positively charged, and all those plus charges don’t like each other (repel). They are trying to get as far away from each other as possible, so they spread far apart. Does the hair continue to stand apart even after you remove the balloon? Does it matter what hair color or texture? (Does the balloon shape matter?)

Bonus Question: How can you get rid of the extra electrons?

Expt. 2: Finding Attraction Rub your head with the balloon and then hold the balloon to a wall. Can you make it stick? How about the ceiling? How many other things does the balloon stick to? (Hint – try a wool sweater.)

Expt. 3 Wiggly Wonder Hold the charged balloon near a stream of water running from a faucet. Can you make the water wiggle without touching it? The charged balloon attracts the stream of water. The water is like a bar magnet in that there are poles on a water molecule: there’s a plus side and a minus side, and the water molecules line up their positive ends toward the balloon when you bring it close.

Expt. 4 Ping Pong Puzzle Rub a comb with a wool sweater, and bring it close to a ping pong ball resting on a flat table. Why do you think the ping pong ball moves? Does it work if you use a charged balloon instead? What if you swap the ping pong ball for a piece of styrofoam?

Expt. 5: Static Neon Store up a good charge of electrons by scuffing along the carpet in socks on a warm, dry day. To make this a much more interesting experiment, hold one end of a neon bulb and watch it light as you touch the other end to a nearby object such as a metal faucet, metal part of a lamp, etc. You can also bring it close to your TV set (the old tube TV kind), both turned on and just turned off, to see if it has any effects on the neon lamp bulb?

Hint: you’ll need to get the neon bulb out of the plastic encasing and hold only one of the wires to make this experiment work – one wire act a as the collector, the other is grounded (via your hand) to the earth. You can also hold onto one lead as you slide down a plastic slide and then touch something grounded (like your mom).

You steal electrons and take on a negative charge when you scuff along the carpet in socks. Remember that just like magnets, ‘like’ charges (negative-to-negative or positive-to-positive) repel, and opposite charges (negative-to-positive) attar, which is why you can make your hair stand up on end by scuffing around a lot. The hairs all become negative, trying to get as far away from each other as they can.

Expt. 6: Electric Tail Feathers Cut a sheet of tissue paper into 12 thin strips, about 1/2″ wide and 8-12″ long. Straighten out a wire coat hanger (snip off the hook part), or find yourself a 10g piece of metal uninsulated wire. Tape the strips to the end of a wire coat hanger (make sure your coat hanger do not have plastic insulation around it – use sandpaper to sand off any clear enamel if you’re not sure). Attach a piece of plastic with tape or clay to the center of the rod, making a V-groove so the handle sits better on the wire. Bring a very charged balloon near the end of the wire – what happens?

Expt. 7: Ghost Words (Although this experiment has also held the name “Ghost Poop”… ) Rub packing peanuts with wool or your hair to build up a strong, quick static charge. Stick the stryfoam to the wall to spell out words. How long do they stay attached to the wall? Does humidity matter? (Try spritzing with a light mist of water).

Expt. 8: Static Bubbles Blow a few big, round bubbles (use store-bought bubble solution, or make your own with 12 cups cold water and 1 cup clear Ivory dish soap and a wire coat hanger stretched into a diamond shape). Chase your bubbles with a charged balloon – what happens? Try the comb rubbed with wool – which works better? What other two things can you use to change the path of the soap bubble? (Photo: Tom Noddy, one of the greatest bubble magicians ever – he’s the first one to ever blow a square bubble.)

Expt. 9: Fluorescents Unplugged In a dark room, rub the length of a fluorescent bulb with a piece of plastic wrap (or polyethylene bag or wool sweater) vigorously and then pull your arm away – the bulb should light up momentarily. What other materials cause it to glow?

Expt. 10: Ghost Leg This experiment is absolutely hilarious to watch, but you must be persistent to get it right. On a cold winter day, crank up the heat in your house to warm and dry out the air. You now have the ideal static electricity environment. Take a nylon stocking (just a single knee-length will work, or just use half of a full pair, but roll up the unused half so it’s out of your way) and press the toe part against a nearby wall. Line your other hand with a piece of a clear plastic bag (if the plastic can stretch, it’s the right kind) and rub the nylon stocking vigorously. Now hold the stocking in the air and see if you scrubbed it well enough to charge the stocking with enough static charge so it repels itself and fills out – looking as if there’s a ghost filling out the leg!

Why do these experiments work?

The triboelectric series is a list that ranks different materials according to how they lose or gain electrons. Near the top of the list are materials that take on a positive charge, such as air, human skin, glass, rabbit fur, human hair, wool, silk, and aluminum. Near the bottom of the list are materials that take on a negative charge, such as amber, rubber balloons, copper, brass, gold, cellophane tape, Teflon, and silicone rubber.

When you rub a glass rod with silk, the glass takes on a positive charge and the silk holds the negative charge. When you rub your head with a balloon, the hair takes on a positive charge and the balloon takes on a negative charge.

When you scuff along the carpet, you build up a static charge (of electrons). Your socks insulate you from the ground, and the electrons can’t cross your sock-barrier and zip back into the ground. When you touch someone (or something grounded, like a metal faucet), the electrons jump from you and complete the circuit, sending the electrons from you to them (or it).

The fluorescent bulb lights up when the electrons jump around. The inside of the bulb is coated with phosphor (a white powder) and filled with mercury vapor gas. The phosphor gives off light whenever it gets smacked with UV light. The mercury vapor gives off UV light whenever it gets excited by electricity (movement of electrons). When you rub the outside of the bulb, electrons start to jump around, exciting the gas, which generated UV light, which hits the phosphor and causes it to glow briefly. When the bulb is in balance, it stays dark. If you tip the balance, electrons flow and you get light.

Exercises

Why does the hair stick to the balloon?
How do you get rid of electrons?
Can you see electrons? Why or why not?
Does it matter what kind of hair you rub the balloon on?
How long does the hair continue to stand up after you remove the balloon?
Does it matter what kind of balloon you use?
How fast or slow do you need to rub for the biggest charge on the balloon?
Does hair color matter?
This evening, find an article or story that describes how electricity improves our lives. Bring the article to school. If you bring in an article that no one else brings in, you get extra points.

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Latest News

Key Concepts

Key Concepts

What’s Going On?

Questions to Ask

Circuits & Components Exercises

Need answers?

Need answers?

Why does metal conduct electricity?

How does it work?

Materials for the Tilt Sensor:

Materials for the Motion Sensor:

Static Electricity Experiments!

Why do these experiments work?