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Static Electricity and Electroscope Experiment Procedures

Have you ever shaken hands with a friend and gotten a small shock? That shock is the result of static electricity. All physical objects are made of atoms that contain electrical charges. Normally, the positive and negative charges within an object are balanced. When the positive and negative charges in an object are imbalanced, static electricity is created. Friction between some objects, such as a shoe on a carpet, create a buildup of electrons (negative charges). When you touch your friend, the surplus electrons are released, and you both get a little shock. Electroscopes measure the presence and strength of electric charges.

Materials List
- To make an electroscope and perform an experiment, you need a medium-size round balloon, already inflated and tied; a foam plate; a foam cup; a plastic drinking straw; modeling clay; aluminum pie plate; thread; masking tape; 1-inch by 1-inch square of aluminum foil; wooden ruler and materials to test, such as polyester, nylon, cotton, silk, wool, plastic wrap, plastic food container, copper, facial tissue or tissue paper.
Making the Electroscope
- Make two holes on opposite sides near the bottom of the cup using a pencil. Push the straw through both holes with one side barely sticking out and the other sticking out as far as possible. Roll four small balls of clay, each about approximately 1/2 inch in diameter. Stick the clay balls to the rim of cup, turn the cup upside down and place it near the inside edge of the aluminum pie plate. The straw should hang out over the edge of the pie plate. Push down on the cup to adhere it to the plate. Cut an 8-inch piece of thread and make several knots close together at one end. Scrunch the foil around the knotted end of the thread to make a ball about the size of a marble. Check that it is tight enough so it won't fall off the thread. Tape the other end of the thread to the overhanging end of the straw. The ball should hang straight down near the outer edge of the pie plate. Tape the other end of the straw to the cup to prevent it from moving. You have just made an electroscope.
Testing the Electroscope
- Rub the balloon on the Styrofoam plate to create some static electricity. This charges the plate, causing electrons to build up on one side. The electrons will remain in place because Styrofoam does not conduct electricity. Hold the electroscope by the cup and place it on top of the Styrofoam plate. The electrons on the foam plate will be conducted by the aluminum pie plate. The negative charges in the pie plate will repel the negative charges in the foil ball, pushing the ball away from the electroscope. Measure and record the distance traveled by the ball. Do not touch the ruler to the electroscope or foil ball. The greater the charge, the farther the ball will travel. Touch your finger to the ball. What happened? In between testing each material, touch the aluminum pie plate to discharge the electroscope.
The Experiment
- Create a chart with three columns: the name of the object, the material the object is made of and the distance between the pan and ball. Test each object with the electroscope and record your results in the chart. Order the objects tested from the most charged (largest distance the ball traveled away from the plate) to the least charged, least distance traveled. This is called a triboelectric series. Can you make any conclusions based on your data?

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