Electricity - Static Power
You're the scientist!
From the previous pages you know that static electricity builds up when you rub a balloon on your shirt or your shoes on the carpet. What other things can be rubbed together to create static electricity? How do different things react to static electricity?
WARNING! Do not do any of these activities near your computer!
- Large clear plastic bags
- Puffed cereal
- Wool cloth
- Place a few pieces of puffed cereal into the plastic bag.
- Inflate the bag by blowing into it like you would to a balloon. Seal the bag with a twist tie or by closing the plastic zipper. Do not do anything to the comb yet.
- Shake the bag to see if the cereal does anything unusual. Bring the comb near the bag and observe.
- Touch the wool cloth to the bag, but do not rub it on the bag. Record your observations.
- Rub the bag with the wool cloth. Record your observations.
- Rub both the plastic bag and the comb with the wool cloth. Bring the wool comb near the plastic bag and observe.
- Open the bag and empty the cereal onto the wool cloth. Place the bag on the wool cloth. Place the cereal back in the plastic bag.
- Inflate the bag and seal as done in step 2. Rub the comb with the wool cloth and bring the comb near the plastic bag. Describe what happens.
How many pairs of shoes and socks do you own? From what materials are they made? In the following activity you will find out more about materials that produce static electricity.
- Shoes with rubber soles
- Shoes with leather soles
- Shoes with synthetic soles
- One pair of wool socks
- One pair of cotton socks
- One pair of synthetic socks (nylon)
- On a dry day, walk sliding your feet on a rug or carpet. Walk as far as you possibly can. Dim the lights so you can observe any sparks you make.
- When you have walked as far as you can, slowly bring your finger close to a metal object, such as a doorknob or a water faucet. Describe what happens.
- Repeat the above procedure with different kinds of shoes and socks, and in your bare feet. Make observations relating to static electricity.
- Is there a relationship between what you have on your feet and the amount of static charge you build up on your body? Which one seems to produce the biggest static charge? The smallest? Most carpets today are made of synthetic fibers, but if you can find one, try the same experiment on a wool carpet. Do you generate more or less of a static charge?
- Try the same experiment on an extremely humid day. Are your results the same?
After walking across carpet, you should always discharge any static built up on your body before touching a computer or floppy disks. A static charge so small you can't even feel it could damage your computer or disk.
Think about it!
During World War II, some workers at Hill Air Force Base, here in Utah, had jobs inspecting cannon cartridges. The inspection was done on a metal table connected to a ground wire. The workers were required to wear cotton underwear and socks. Why do you suppose this was required?
This activity can be messy, but if you are careful you will not have to do a lot of cleaning afterward.
Again do not do this activity near your computer!
- Rubber balloons
- Salt or sand
- Tiny pieces of paper, foil, or polystyrene
- Wool cloth
- Silk cloth
- Nylon or other synthetic cloth
- Cotton cloth
- Ruler (metric)
- Measuring cup (metric)
- Unfold a full page from a newspaper and place it on your table or desk. Keep all the sand, salt, and tiny pieces of materials on this paper.
- Place a thin layer of sand or salt on the newspaper. Inflate your balloon and tie it off.
- Rub the balloon with the wool cloth. Count the number of times you rub it.
- Slowly bring the balloon down toward the salt or sand. Record what happens.
- Measure the distance in millimeters, the bottom of the balloon is above the surface of your table or desk and record your data.
- Repeat the above procedure, bringing the balloon down slowly above piles of pieces of paper, foil, and polystyrene. Measure the distances to your table or desk the balloon is before anything happens. Does the size of the pieces have anything to do with what happens?
- Get a new balloon, and repeat the activity; but this time rub the balloon with a different kind of fabric. Rub it the same number of times as you rubbed it with the wool fabric. What are your results now? Does the same thing happen at the same height above the table or desk? Are there some kinds of fabric which build up more of a charge on the balloon? Are there some that do not charge it at all? Try it with a balloon which has not been rubbed with anything at all. Be sure to use a different balloon for each fabric so there is no effect left on the balloon from the previous fabric. What happens if you bring the fabric instead of the balloon near the substances?
- Select the fabric which worked best. Change the number of times you rub the balloon. Do you get the same effect if you rub the balloon once as you do if you rub it several times? Explain your answer.
To measure how much salt or sand is attracted to a balloon do the following:
- Measure 10 cc of salt or sand and pour it on the newspaper. Spread it in a thin ltayer.
- Rub the balloon once, then hold it above the newspaper. Measure the amount of salt or sand left by pouring it back into your 10 cc container. Record the amount.
- Pour another 10 cc of salt or sand on the newspaper and repeat the experiment, but this time rub the balloon ten times. Predict what will happen and record your observations. Continue the experiment increasing the number of times the balloon is rubbed by 10 each time. Record your observations and graph the results.
Predict what you think will happen if you dampen the salt, sand, paper, foil, and polystyrene foam. Design and perform an experiment to determine if you were correct.
Think about it!
What did you learn? What "rules" did you discover about how static electricity works? Answer the following questions.
- List three kinds of materials that, when rubbed together, do not create static electricity.
- List three types of materials that, when rubbed together, create static electricity.
- What types of materials are attracted to objects with static electricity?
- What types of materials are repelled by objects with static electricity?