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

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

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