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Project Summary

Difficulty	3
Time required	Very Short (a day or less)
Prerequisites	None
Material Availability	Readily available
Cost	Very Low (under $20)
Safety	When working with electricity, take precautions and beware of electric shock.

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Objective

In this experiment you will make an electroscope to test the presence of static electricity in different types of materials and formulate a triboelectric series, an ordered list which describes the type of charge an object has as a result of static electricity.

Introduction

Static electricity is the build-up of electrical charge in an object. Sometimes static electricity can suddenly discharge, like when a bolt of lightning flashes through the sky. Other times, static electricity can cause objects to cling to each other, like socks fresh out of the dryer. The static cling is an attraction between two objects with different charges, positive (+) and negative (−).

You can create static electricity by rubbing one object against another object. The rubbing produces friction which releases negative charges, called electrons, that build up to produce a static charge. When you shuffle your feet across a carpet the friction causes a static charge to build up inside of you. You can suddenly discharge this static electricity when you touch a friend to send them a shock. When you rub a balloon on your head the friction causes opposite static charges to build up in your hair and in the balloon. You can see these two opposite static charges attracting each other when you pull the balloon slowly away from your head making your hair stand up.

Static electricity makes your hair stand up! (NASA, 2004)

How can static electricity be measured? One way is to use an electroscope. In this experiment you will build an electroscope to test several objects made out of different materials to see which ones conduct the most static electricity. Then you will put your results together to formulate a triboelectric series, an ordered list which describes the type of charge an object has as a result of static electricity. The results may shock you!

Terms, Concepts and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the Internet, or take you to your local library to find out more!

• static electricity
• electrons
• neutral
• charged
• friction

• How can static electricity be measured?
• How do different materials react to static electricity?
• Which materials are neutral and which ones are charged?

Bibliography

• This idea was adapted from a project on how to build an electroscope on the ZOOM science activities website hosted by PBS Kids:
  PBS Kids, 2004. "ZOOMsci: Electroscope" WGBH Educational Foundation, Boston, MA. [3/28/06] http://pbskids.org/zoom/activities/sci/electroscope.html
• Science Made Simple, 2005. "Static Electricity: What Causes Static Shocks?" Voorhees, NJ: Science Made Simple, Inc. [accessed: 3/18/06] http://www.sciencemadesimple.com/static.html
• Loney, D., 2006. "Hair-Raising Science: Static Electricity," American Chemical Society. [accessed: 3/18/06] http://www.chemistry.org/portal/a/c/s/1/feature_tea.html?id=be98b66208ff11d6f2406ed9fe800100
• NASA, 2004. "Runaway Soda," Kids Features, National Aeronautics and Space Administration (NASA). [accessed: 3/18/06] http://www.nasa.gov/audience/forkids/activities/A_Runaway_Soda.html
• Brynie, F.H., 2005. Parents Crash Course: Elementary School Science Fair Projects, Hoboken, NJ: Wiley Publishing Inc. pp 124-130.

Materials and Equipment

• balloon
• foam plate
• foam cup
• drinking straw
• clay
• aluminum pie pan
• thread
• aluminum foil
• masking tape
• wooden ruler
• several different materials to test (polyester, nylon, cotton, wool, silk, aluminum, saran wrap, plastic, copper, tissue paper, almost anything!)

Experimental Procedure

1. First you will make an electroscope to test for the presence of static electricity in different materials.

   The electroscope at rest.

2. Make two holes near the bottom of a styrofoam cup on opposite sides. A good way to do this is by pushing a sharp pencil, chop-stick or skewer through the cup.
3. Push a plastic straw through the holes in the cup. Push the straw so that it is almost flush with the cup on one side, but sticking out as much as possible on the other.
4. Stick 4 little balls of clay to the rim of the cup, each about 1/2 inch in diameter.
5. Turn the cup upside down and and stick it to the bottom of the aluminum pie pan using the clay. Make sure that the cup is right at the edge so that the straw sticks out over the edge of the pan.
6. Cut a piece of thread about 8 inches long and tie a few knots in one end of the thread.
7. Cut a one-inch square of aluminum foil. Use it to make a ball around the knots in the thread. The ball should be about the size of a marble. It should be just tight enough so it doesn't fall off the thread.
8. Tape the other end of the thread to the tip of the straw so that the ball of foil hangs straight down from the straw, right next to the edge of the pan.
9. Tape the straw to the cup so it doesn't move around when you use the electroscope.
10. To test the electroscope, create some static electricity. An easy way to create static is by rubbing a balloon on a styrofoam plate. When you do this, you "charge" the plate, which means you cause a buildup of electrons on one side. Even though the plate is charged, the electrons don't move because styrofoam doesn't conduct electrons.
11. Once you've created some static electricity, place the electroscope on top of the styrofoam plate. Be sure to hold the electroscope by the foam cup and not the aluminum pan, otherwise it won't work. Electrons move easily through the metal, so when you put the pie pan onto the charged foam plate, the electrons travel into the pan. The added negative charges on the pan repel the negative charges on the foil ball, which moves away from the pan.

    When the electroscope is negatively charged, the foil ball is repelled by the foil plate.

12. You can use a ruler to measure the distance between the foil ball and the pan. The more charge there is, the more distance there will be. Be careful not to touch the ball or the edge of the plate with the ruler when you measure.
13. Now, touch the ball with your finger. What happens?
14. Now that you know your electroscope works, you will use it to test the static electricity present in different materials. Between each experiment you will need to discharge your electroscope by touching the pan with your finger or a metal rod.
15. Try charging different objects with static electricity and testing them with the electroscope. Good materials to try are plastic wrap, a comb, different types of fabric, aluminum foil. Write the objects you will test in a table:

    Object	Type of Material	Distance Between Ball and Pan (cm)
    Comb
    Wool Scarf
    Aluminum Foil
    Saran Wrap
    etc...

16. Test each object with the electroscope and measure the distance between the ball and the edge of the plate. Write your data in the table and compare your results. Which objects hold an electric charge? Which don't?
17. Now, use your data to order the objects from most charged (largest distance between ball and plate) to least charged (smallest distance between ball and plate). This is a Triboelectric Series, and can be written as an ordered list or chart. How do common objects rank? Can you compare your Triboelectric Series to others you find on the Internet? How do they compare? What are some differences?

Variations

• Some objects become negatively charged and other objects become positively charged with static electricity. Does this kind of electroscope detect both types? How can you tell the difference between the two? Try to discover a way to sort the charged items into positively and negatively charged items.
• Static electricity is formed when free electrons are knocked loose by friction. Conduct an experiment to test if the amount of static electricity formed is related to the amount of friction. See the related project, Rubbing Up Against Static Electricity.
• Static electricity is not good when it gets in your clothes! How do dryer sheets work? Try an experiment rubbing the object with a dryer sheet (like Bounce) after rubbing against the wool. What happens to the electroscope reading? Can you detect a difference before and after contact with the dryer sheet? If so, you can compare the results from different products. How do they compare? Which brands are most effective?
• For a more advanced experiment, try investigating static electricity in different conditions, temperatures and humidities (Brynie, 2005).

• For more science project ideas in this area of science, see Electricity & Electronics Project Ideas.

Credits

Sara Agee, Ph.D., Science Buddies

This idea was adapted from a project on how to build an electroscope on the ZOOM science activities website hosted by PBS Kids:
PBS Kids, 2004. "ZOOMsci: Electroscope" WGBH Educational Foundation, Boston, MA. [3/28/06] http://pbskids.org/zoom/activities/sci/electroscope.html

Last edit date: 2006-04-20 13:02:19

Career Focus

If you like this project, you might want to think about career opportunities in Electricity & Electronics.

Electricians are the people who bring electricity to our homes, schools, businesses, public spaces, and streets—lighting up our world, keeping the indoor temperature comfortable, and powering TVs, computers, and all sorts of machines that make life better. Electricians install and maintain the wiring and equipment that carries electricity, and they also fix electrical machines. Learn more about this career: Electrician.