Static Electricity

INTRODUCTION

Opposites attract. The power of static electricity can be seen by watching oppositely charged objects attract each other or objects with like charges repel. These charges cannot be seen, but their effects can be.A charged balloon can make your hair stick up or push another balloon away. You can use static electricity to make bubbles stay in the air or to guide a Ping-Pong ball around a table without even touching it.

MATERIALS

• Balloons
• String
• Paper
• Plastic comb
• Wool
• Ping-pong balls
• Puffed rice
• Soap bubbles
• Salt and pepper

WHAT TO DO

1. Blow up a balloon and ask a student to rub it on his or her head. This will give the balloon a negative charge because it picks up electrons from the student’s hair. The hair, now missing some electrons, will be positively charged. The positive charge on the hair and the negative charge on the balloon attract each other, so the hair stands up toward the balloon.
2. Cut paper into very small pieces and make a pile on a desktop or table. Charge a balloon by rubbing it in someone’s hair or by rubbing it with a piece of wool. Hold the charged balloon just above the pile of paper pieces and the paper will jump. First, the paper will be attracted to the negative charge on the balloon so it will jump up and stick to the balloon. But by coming into contact with the balloon the paper picks up some of the negative charge. Since like charges repel, the paper will then jump off of the balloon.
3. Blow up two balloons and tie a separate piece of string around the knot in each of them. Attach one balloon to the underside of a desk or table by taping the string. Make sure the balloon can hang without touching anything else. Rub the hanging balloon with wool to charge it. Charge the second balloon the same way, then hold it by the string. Move the free balloon near the hanging balloon and watch them push away from each other. Their negative charges repel. If a piece of paper is placed between the two balloons they will come together quickly because they will both be attracted to the paper. Remove the paper and they will again repel each other.
4. Charge a plastic comb by rubbing it with wool. Bring the comb near a Ping-Pong ball on a tabletop and slowly move the comb around. Because the ball is attracted to the negative charge on the comb, the ball will follow the comb.
5. Charge a plastic comb by rubbing it with wool. Blow a few soap bubbles into the air and bring the charged comb near one of the bubbles. The bubble will be attracted to the charge on the comb, so with practice the comb can be used to keep the bubble in the air without popping.
6. Catch a soap bubble on the end of the bubble-blowing wand and slowly bring a charged comb or balloon near it. Watch as the bubble distorts and stretches toward the charge until it finally detaches from the wand and pops when it slams into the comb.
7. Separate a mixture of salt and pepper quickly, without touching it by holding a charged comb or balloon over the mixture and slowly bringing it closer. The lighter pepper will be picked up and the heavier salt will be left behind.

QUESTIONS

1. Why does your hair stick up when you rub a balloon on it?
2. What else can you make a balloon stick to? How? Why?
3. How can you move a Ping-Pong ball without touching it or the table it is sitting on? How else could this new skill be used?
4. What other tricks can you do using static electricity?
5. Why do the bubbles move and stretch toward the charged balloon or comb?
6. Why is the pepper picked up but not the salt? If there were not any pepper, would the salt be picked up?

SOURCES

"Edison Etc." The Wild Goose Company: Salt Lake City, 1994, p. 41-43.
"The Science Book of Electricity." Neil Ardley, Harcourt Brace and Company: London, 1991, p. 20-21.

© S. Olesik, WOW Project, Ohio State University, 2001.