Balloons and Static Electricity

Contributed by Sabrina Brickner

Introduction

• How does charge work? Can we really see how electrons work without fancy science tools?

Materials

• Balloons
• Someone with hair on their head
• A working faucet
• An empty metal can

Procedure

1. Blow up a balloon.
2. Rub it on your head.
3. Watch what happens to the balloon and your hair.
4. Turn on your sink and put the balloon close to the water without letting the balloon touch the water.
5. Watch what happens to the stream of water. 
6. Try moving the balloon around a little bit (without touching the water) and see what happens.
7. Get an empty metal can and lie it on a hard surface (like the floor or a kitchen counter) such that it can roll. 
8. Put the balloon close to the can without touching them together.
9. Slowly move the balloon away from the can and see what happens.

Physics Concepts and Questions

How does this work?

Static electricity arises from an electrical charge imbalance. In this experiment, when we rub the balloon against our hair, we transfer negative charge to the balloon in the form of electrons. This means that the balloon is now negatively charged, and our hair is positively charged. When we put the balloon by our hair, they attract because they are oppositely charged. This same idea of opposites attracting applies to the water coming out of the faucet, and the empty metal can. 

How can the water be positively charged if we haven’t done anything to it like we did in the case of rubbing the balloon on our hair which makes our hair positively charged?

When water comes out of the faucet it is neutral, meaning that it has positive and negative charges in it. However, when we bring the balloon close to the water, some of the negative charge is repelled away into other parts of the water (the top and bottom of the stream), leaving the middle of the stream of water (by the balloon) positively charged. Since this part of the water is positively charged, and the balloon is negatively charged, they attract.

What about the metal can? Can electrons really travel through metal like they travel through water?

Yes they can! The same thing happens here! Some of the positive charge in the can goes to the other side of the can, leaving the side facing the balloon positively charged. Thus the balloon and the can attract. 

Conclusions and Further Investigations

• If you rub the balloon on your head 2 times, does it bend the water more, less, or about the same as rubbing the balloon on your head 10 times?
• Does the temperature of the water make a difference?