Special Science Teleclass: Magnetism

Saturday April 18, 2020
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!

Discover how to detect magnetic fields, learn about the Earth's 8 magnetic poles, and uncover the mysterious link between electricity and magnetism that marks one of the biggest discoveries of all science…ever.

Materials:
  • Box of paperclips
  • Two magnets (make sure one of them ceramic because we're going to break it)
  • Compass
  • Hammer
  • Nail
  • Sandpaper or nail file
  • D cell battery
  • Rubber band
  • Magnet Wire
Optional Materials if you want to make the Magnetic Rocket Ball Launcher:Four ½” (12mm) neodymium magnets
  • Nine ½” (12 mm) ball bearings
  • Toilet paper tube or paper towel tube
  • Ruler with groove down the middle
  • Eight strong rubber bands
  • Scissors


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Key Concepts

While the kids are playing with the experiments see if you can get them to notice these important ideas. When they can explain these concepts back to you (in their own words or with demonstrations), you’ll know that they’ve mastered the lesson.

Magnets
  • Magnetic fields are created by electrons moving in the same direction. Electrons can have a “left” or “right” spin. If an atom has more electrons spinning in one direction than in the other, that atom has a magnetic field.
  • If an object is filled with atoms that have an abundance of electrons spinning in the same direction, and if those atoms are lined up in the same direction, that object will have a magnetic force.
  • A field is an area around an electrical, magnetic or gravitational source that will create a force on another electrical, magnetic or gravitational source that comes within the reach of the field.
  • In fields, the closer something gets to the source of the field, the stronger the force of the field gets. This is called the inverse square law.
  • A magnetic field must come from a north pole of a magnet and go to a south pole of a magnet (or atoms that have turned to the magnetic field.)
  • All magnets have two poles. Magnets are called dipolar which means they have two poles. The two poles of a magnet are called north and south poles. The magnetic field comes from a north pole and goes to a south pole. Opposite poles will attract one another. Like poles will repel one another.
  • Iron and a few other types of atoms will turn to align themselves with the magnetic field. Over time iron atoms will align themselves with the force of the magnetic field.
  • The Earth has a huge magnetic field. The Earth has a weak magnetic force. The magnetic field comes from the moving electrons in the currents of the Earth’s molten core. The Earth has a north and a south magnetic pole which is different from the geographic north and south pole.
  • Compasses turn with the force of the magnetic field.
Electromagnetism
  • Electricity is moving electrons. Magnetism is caused by moving electrons. Electricity causes magnetism.
  • Magnetic fields can cause electricity.

What's Going On?

The scientific principles we’re going to cover were first discovered by a host of scientists in the 19th century, each working on the ideas from each other, most prominently James Maxwell. This is one of the most exciting areas of science, because it includes one of the most important scientific discoveries of all time: how electricity and magnetism are connected. Before this discovery, people thought of electricity and magnetism as two separate things.  When scientists realized that not only were they linked together, but that one causes the other, that’s when the field of physics really took off.

Questions

When you’ve worked through most of the experiments ask your kids these questions and see how they do:
  1. How many poles do magnets have, and what are they?
  2. What happens when you bring two like poles together?
  3. How do I know which pole is which on a magnet?
  4. Is the magnetic force stronger or weaker the closer a magnet gets to another magnet?
  5. What kinds of materials are magnets made from?
  6. Name three objects that stick to a magnet.
  7. Name three that don’t stick to a magnet.
  8. What does a compass detect? How do you know when it’s detected it?
Answers:
  1. How many poles do magnets have, and what are they? Two. North and South poles.
  2. What happens when you bring two like poles together? They repel each other.
  3. How do I know which pole is which on a magnet? Put two magnets together and find the spot where they are repelling the strongest. The poles facing each other are the same. Or bring it close to a compass. If the magnet attracts the needle to north, then the magnet’s pole is the south pole.
  4. Is the magnetic force stronger or weaker the closer a magnet gets to another magnet? Stronger.
  5. What kinds of materials are magnets made from? Iron, nickel and cobalt.
  6. Name three objects that stick to a magnet. Paperclips, pipe cleaners, and staples.
  7. Name three that don’t stick to a magnet. US quarter, glass, plastic.
  8. What does a compass detect? How do you know when it’s detected it? The direction of a magnetic field. When the needle is deflected, the compass is in a magnetic field.
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Special Science Teleclass: Magnetism

Monday October 20, 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!


Discover how to detect magnetic fields, learn about the Earth’s 8 magnetic poles, and uncover the mysterious link between electricity and magnetism that marks one of the biggest discoveries of all science…ever.


Materials:


  • Box of paperclips
  • Two magnets (make sure one of them ceramic because we’re going to break it)
  • Compass
  • Hammer
  • Nail
  • Sandpaper or nail file
  • D cell battery
  • Rubber band
  • Magnet Wire

Optional Materials if you want to make the Magnetic Rocket Ball Launcher:Four ½” (12mm) neodymium magnets


  • Nine ½” (12 mm) ball bearings
  • Toilet paper tube or paper towel tube
  • Ruler with groove down the middle
  • Eight strong rubber bands
  • Scissors

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Key Concepts

While the kids are playing with the experiments see if you can get them to notice these important ideas. When they can explain these concepts back to you (in their own words or with demonstrations), you’ll know that they’ve mastered the lesson.


Magnets


  • Magnetic fields are created by electrons moving in the same direction. Electrons can have a “left” or “right” spin. If an atom has more electrons spinning in one direction than in the other, that atom has a magnetic field.
  • If an object is filled with atoms that have an abundance of electrons spinning in the same direction, and if those atoms are lined up in the same direction, that object will have a magnetic force.
  • A field is an area around an electrical, magnetic or gravitational source that will create a force on another electrical, magnetic or gravitational source that comes within the reach of the field.
  • In fields, the closer something gets to the source of the field, the stronger the force of the field gets. This is called the inverse square law.
  • A magnetic field must come from a north pole of a magnet and go to a south pole of a magnet (or atoms that have turned to the magnetic field.)
  • All magnets have two poles. Magnets are called dipolar which means they have two poles. The two poles of a magnet are called north and south poles. The magnetic field comes from a north pole and goes to a south pole. Opposite poles will attract one another. Like poles will repel one another.
  • Iron and a few other types of atoms will turn to align themselves with the magnetic field. Over time iron atoms will align themselves with the force of the magnetic field.
  • The Earth has a huge magnetic field. The Earth has a weak magnetic force. The magnetic field comes from the moving electrons in the currents of the Earth’s molten core. The Earth has a north and a south magnetic pole which is different from the geographic north and south pole.
  • Compasses turn with the force of the magnetic field.

Electromagnetism


  • Electricity is moving electrons. Magnetism is caused by moving electrons. Electricity causes magnetism.
  • Magnetic fields can cause electricity.

What’s Going On?

The scientific principles we’re going to cover were first discovered by a host of scientists in the 19th century, each working on the ideas from each other, most prominently James Maxwell. This is one of the most exciting areas of science, because it includes one of the most important scientific discoveries of all time: how electricity and magnetism are connected. Before this discovery, people thought of electricity and magnetism as two separate things.  When scientists realized that not only were they linked together, but that one causes the other, that’s when the field of physics really took off.


Questions

When you’ve worked through most of the experiments ask your kids these questions and see how they do:


  1. How many poles do magnets have, and what are they?
  2. What happens when you bring two like poles together?
  3. How do I know which pole is which on a magnet?
  4. Is the magnetic force stronger or weaker the closer a magnet gets to another magnet?
  5. What kinds of materials are magnets made from?
  6. Name three objects that stick to a magnet.
  7. Name three that don’t stick to a magnet.
  8. What does a compass detect? How do you know when it’s detected it?

Answers:


  1. How many poles do magnets have, and what are they? Two. North and South poles.
  2. What happens when you bring two like poles together? They repel each other.
  3. How do I know which pole is which on a magnet? Put two magnets together and find the spot where they are repelling the strongest. The poles facing each other are the same. Or bring it close to a compass. If the magnet attracts the needle to north, then the magnet’s pole is the south pole.
  4. Is the magnetic force stronger or weaker the closer a magnet gets to another magnet? Stronger.
  5. What kinds of materials are magnets made from? Iron, nickel and cobalt.
  6. Name three objects that stick to a magnet. Paperclips, pipe cleaners, and staples.
  7. Name three that don’t stick to a magnet. US quarter, glass, plastic.
  8. What does a compass detect? How do you know when it’s detected it? The direction of a magnetic field. When the needle is deflected, the compass is in a magnetic field.

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Electromagnetic Crane

Sunday April 13, 2014

An electromagnet is a magnet you can turn on and off using electricity. By hooking up a coil of wire up to a battery, you will create an electromagnet. When you disconnect it, it turns back into a coil of wire. Since moving electrons cause a magnetic field, when connecting the two ends of your wire up to the battery, you caused the electrons in the wire to move through the wire in one direction. Since many electrons are moving in one direction, you get a magnetic field!
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Materials:


  • Nail
  • Wood skewer
  • Magnet wire
  • D cell battery
  • Sandpaper or nail file
  • 2 rubber bands
  • Foam block
  • 2 fat popsicle sticks
  • Paperclips
  • Drill
  • Hot glue or tape


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Ferrofluid

Friday July 1, 2011

A ferrofluid becomes strongly magnetized when placed in a magnetic field. This liquid is made up of very tiny (10 nanometers or less) particles coated with anti-clumping surfactants and then mixed with water (or solvents). These particles don’t “settle out” but rather remain suspended in the fluid.


The particles themselves are made up of either magnetite, hematite or iron-type substance.


Ferrofluids don’t stay magnetized when you remove the magnetic field, which makes them “super-paramagnets” rather than ferromagnets. Ferrofluids also lose their magnetic properties at and above  their Curie temperature points.


Ferrofluids are what scientists call “colloidal suspensions”, which means that the substance has properties of both solid metal and liquid water (or oil), and it can change phase easily between the two. (We as show you this in the video below.) Because ferrofluids can change phases when a magnetic field is applied, you’ll find ferrofluids used as seals, lubricants, and many other engineering-related uses.


Here’s a video on toner cartridges and how to make your own homemade ferrofluid. It’s a bit longer than our usual video, but we thought you’d enjoy the extra content.


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Download Student Worksheet & Exercises


Engineering and scientists use ferrofluids to make a liquid seal in hard disks around the spinning disks to keep out dust and grit (hard drives must be kept exceptionally clean!). They do this by adding a layer of ferrofluid between the rotating shaft and magnets which surround the shaft.


You can also use ferrofluids to reduce friction, the way ice and water are used in ice skating rinks. If you coat a strong magnet with ferrofluid, you can get it to glide across a smooth surface like a hockey puck.


NASA uses ferrofluids in the flight instruments for spacecraft, also!


Each particle of ferrofluid is like a each grain or a micro-magnet, which not only interacts with magnetic fields, but also with light.


With loudspeakers, the large magnets that interacting with the coil often heat up. If we replace the magnet with ferrofluid (which is a liquid, remember!) it will actively conduct the heat away from the coil and cool it down because cold ferrofluid is more strongly attracted than hot, and thus the cooler fluid flows toward the coil, and the warmer fluid moves away from the coil.


Exercises


  1. Is the ferrofluid a solid or a liquid?
  2. Does the strength of a magnet matter?
  3. What would happen if the magnet went over the rim of the cup?
  4. Does the ferrofluid have a north and south pole?
  5. What happens if you bring a compass near the ferrofluid?
  6. Name three specific ways ferrofluid makes our lives easier. How might you use a ferrofluid if you were inventing something?

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Electromagnets Exercises

Sunday April 4, 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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(Don’t be fooled by the small number of questions here… if you can answer these accurately, you’ve mastered the lesson.)


1. How does a moving magnet make electricity?
2. What’s an electromagnet?
3. How does the DC motor you built work?
4. What is a reed switch?
5. How does a magnet make sound?


Need answers?

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Magnets Exercises

Sunday April 4, 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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1. What happens when you break a magnet in half? Can you separate the North and South poles?
2. What causes magnetism?
3. Why does your refrigerator magnet stick to the fridge door?
4. Is aluminum magnetic, electrically conductive, or both?
5. What elements would you guess to be in a magnet? Can you name three?
6. What causes (or creates) magnetic field?
7. Name the biggest magnet you can think of.
8. Where is the magnetic south pole?
9. What happens when you heat up a magnet?
10. Why is the grape repelled by the magnet?
11. Why does the magnet go slowly down the ramp?


Need answers?

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Answers to Electromagnetism Exercises

Sunday April 4, 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. If you moved that magnet back and forth along a wire-wrapped nail fast enough you could power a light bulb. (However, by fast enough, I mean like 1000 times a second or more!)


2. A magnet that you can turn on and off using electricity. An example is a nail wrapped in a coil of wire, powered by a battery pack.


3. The coil is magnetized (becomes an electromagnet) and is momentarily attracted to the permanent magnet and starts to align itself with it, but as it does, it breaks the connection and the coil becomes just a piece of unmagnetized wire, which continues to rotate from the previous pull (when it was magnetic). As it does, the coil energizes again, now repelling itself and pushing itself away as it tries to align itself with the magnet again, and as it does, the electricity goes off again, allowing the coil to rotate freely (and not get stuck in one position). And on it goes.


4. It’s a switch that connects (turns on) when a magnet is close by. The two small steel plates hit each other and allow electricity to flow.


5. Magnetism can create electricity and electricity can create magnetism. Sound is vibrations. To make a speaker, we need to somehow make something vibrate. The radio provides the electricity that gets pumped through the wires. The radio very quickly pumps electricity in one direction and then switches to pump it in the other direction. This movement of electrons back and forth creates a magnetic field in the coil of wire. Since the electricity keeps reversing, the magnetic field keeps reversing. Basically, the poles on the electromagnet formed by the coil go from north to south and back again. Since the poles keep reversing, the permanent magnet you have taped to the cup keeps getting attracted, then repelled, attracted, then repelled. This causes vibrations. The speaker cone (or cup, as in the speaker we’re going to make) that’s strapped to the coil and magnet acts as a sound cone. The magnet causes the sound cone to vibrate and since it’s relatively large, it causes air to vibrate. This is the sound that you hear.


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Answers to Magnets Exercises

Sunday April 4, 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. You get two smaller magnets, each with their own north and south pole. You cannot separate the north and south pole of a manget.


2. Electrons. More accurately, a majority of electrons moving in a similar direction creates a magnetic field.


3. Electrons move on their own. They move around the nucleus and they spin. It’s the electron spin that tends to be responsible for the magnetic field in those “permanent” magnets (the magnets that maintain a magnetic field without electricity flowing).


4. Aluminum conducts electricity, but is not magnetic as detectable by the human eye (called ferromagnetic). Aluminum is technically paramagnetic (very weakly attracted to both poles of a magnet).


5. Iron, nickel, and cobalt are ferromagnetic (attracted to both poles of the magnet).


6. A magnetic field is something I can’t tell you about – it just is (like gravity). Best thing I can do is tell you that a field is an area around an electrical, magnetic or gravitational source that will create a force on another electrical, magnetic or gravitational source that comes within the reach of the field.


7. The earth. On a universe-scale, magnetars (magnetized neutron stars) are the biggest known magnets out there.


8. Off the coast of Antarctica in the ocean.


9. When you heat a magnet past the ‘Curie Temperature’, the magnet loses its magnetism. Once cooled back down, it will regain magnetism again.


10. The grape contains sugar water, which is diamagnetic (repelled by both poles).


11. The eddy currents in the metal plate created by the moving (sliding) magnet slow down the magnet and counteracts gravity.


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Galvanometers

Sunday April 4, 2010

Galvanometers are coils of wire connected to a battery. When current flows through the wire, it creates a magnetic field. Since the wire is bundled up, it multiplies this electromagnetic effect to create a simple electromagnet that you can detect with your compass.
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Here’s what you need to do:


Materials:


  • magnet wire
  • sand paper
  • scissors
  • compass
  • AA battery case
  • 2 AA batteries
  • 2 alligator clip wires


Download Student Worksheet & Exercises


1. Remove the insulation from about an inch of each end of the wire. (Use sandpaper if you’re using magnet wire.)


2. Wrap the wire at least 30-50 times around your fingers, making sure your coil is large enough to slide the compass through.


3. Connect one end of the wire to the battery case wire.


4. While looking at the compass, repeatedly tap the other end of the wire to the battery. You should see the compass react to the tapping.


5. Switch the wires from one terminal of the battery to the other. Now tap again. Do you see a difference in the way the compass moves?


You just made a simple galvanometer. “Oh boy, that’s great! Hey Bob, take a look! I just made a….a what?!?” I thought you might ask that question. A galvanometer is a device that is used to find and measure electric current. “But, it made a compass needle move…isn’t that a magnetic field, not electricity?” Ah, yes, but hold on a minute. What is electric current…moving electrons. What do moving electrons create…a magnetic field! By the galvanometer detecting a change in the magnetic field, it is actually measuring electrical current! So, now that you’ve made one let’s use it!


More experiments with your galvanometer

You will need:


  • Your handy galvanometer
  • The strongest magnet you own
  • Another 2 feet or more of wire
  • Toilet paper or paper towel tube

1. Take your new piece of wire and remove about an inch of insulation from both ends of the wire.


2. Wrap this wire tightly and carefully around the end of the paper towel tube. Do as many wraps as you can while still leaving about 4 inches of wire on both sides of the coil. You may want to put a piece of tape on the coil to keep it from unwinding. Pull the coil from the paper towel tube, keeping the coil tightly wrapped.


3. Hook up your new coil with your galvanometer. One wire of the coil should be connected to one wire of the galvanometer and the other wire should be connected to the other end of the galvanometer.


4. Now move your magnet in and out of the the coil. Can you see the compass move? Does a stronger or weaker magnet make the compass move more? Does it matter how fast you move the magnet in and out of the coil?


Taa Daa!!! Ladies and gentlemen you just made electricity!!!!! You also just recreated one of the most important scientific discoveries of all time. One story about this discovery, goes like this:


A science teacher doing a demonstration for his students (can you see why I like this story) noticed that as he moved a magnet, he caused one of his instruments to register the flow of electricity. He experimented a bit further with this and noticed that a moving magnetic field can actually create electrical current. Thus tying the magnetism and the electricity together. Before that, they were seen as two completely different phenomena!


Now we know, that you can’t have an electric field without a magnetic field. You also cannot have a moving magnetic field, without causing electricity in objects that electrons can move in (like wires). Moving electrons create a magnetic field and moving magnetic fields can create electric currents.


“So, if I just made electricity, can I power a light bulb by moving a magnet around?” Yes, if you moved that magnet back and forth fast enough you could power a light bulb. However, by fast enough, I mean like 1000 times a second or more! If you had a stronger magnet, or many more coils in your wire, then you could make a greater amount of electricity each time you moved the magnet through the wire.


Believe it or not, most of the electricity you use comes from moving magnets around coils of wire! Electrical power plants either spin HUGE coils of wire around very powerful magnets or they spin very powerful magnets around HUGE coils of wire. The electricity to power your computer, your lights, your air conditioning, your radio or whatever, comes from spinning magnets or wires!


“But what about all those nuclear and coal power plants I hear about all the time?” Good question. Do you know what that nuclear and coal stuff does? It gets really hot. When it gets really hot, it boils water. When it boils water, it makes steam and do you know what the steam does? It causes giant wheels to turn. Guess what’s on those giant wheels. That’s right, a huge coil of wire or very powerful magnets! Coal and nuclear energy basically do little more than boil water. With the exception of solar energy almost all electrical production comes from something huge spinning really fast!


Exercises


  1. Why didn’t the coil of wire work when it wasn’t hooked up to a battery? What does the battery do to the coil of wire?
  2. How does a moving magnet make electricity?
  3. What makes the compass needle deflect in the second coil?
  4. Does a stronger or weaker magnet make the compass move more?
  5. Does it matter how fast you move the magnet in and out of the coil?

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Eddy Currents and Magnetic Brakes

Sunday April 4, 2010

Eddy currents defy gravity and let you float a magnet in midair. Think of eddy currents as brakes for magnets. Roller coasters use them to slow down fast-moving cars on tracks and in free-fall elevator-type rides.


Here’s what you need to do this activity:


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Find a thick piece of metal, like copper or aluminum to work with your neodymium magnets.


Materials:


  • aluminum block (the thicker the better, although you can try a cookie sheet)
  • neodymium disc magnets

When you have your parts, you can watch the video:




What’s going on? Here’s the basic idea: when a magnet moves near an object that conducts electricity (usually metal), it creates electric currents called eddy currents which start to flow in the conductor. These eddy currents create magnetic fields (electricity causes magnetism, remember?) in the opposite direction of the moving magnet, slowing an object down so it appears to float.


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