Stickers: How is Static Electricity Produced?

Problem

How is static electricity produced?

Materials

• 9-inch (23-cm) round balloon
• ruler
• scissors
• sewing thread
• masking tape
• hand soap
• water towel
• adult helper and a hair dryer if the air is humid

Procedure

NOTE: This experiment works best on a dry day. If the air is very humid, ask an adult to dry the balloon with a hair dryer.

1. Inflate the balloon and knot the end.
2. Tie a 12-inch (30-cm) piece of thread to the balloon.
3. Tape the free end of the string to the edge of a table.
4. Wash and dry your hands. Your hands must be clean and very dry.
5. Sit on the floor near the balloon.
6. Hold the balloon in one hand and quickly rub the other hand back and forth across the surface of the balloon eight to ten times.
7. Release the balloon and allow it to hang freely.
8. Hold the hand rubbed against the balloon near and to the side of, but not touching, the balloon.

Results

The balloon moves toward your hand. The balloon actually moves upward through the air to reach your hand.

Why?

Static electricity is the build-up of electric charges on an object. These charges are called static charges because they are stationary (not moving). These static charges can be positive or negative. All substances are made up of atoms. Every atom has a nucleus containing protons and electrons spinning around it. The protons have a positive electrical charge, and the electrons have a negative charge. When two substances such as the balloon and your hand are rubbed together, electrons are pulled over from the material that has the weaker attraction for them (the hand) and attach to the material that has the stronger attraction (the balloon). This causes both materials to become charged. The material losing electrons becomes positively charged and the material gaining electrons becomes negatively charged. The diagram shows that the balloon and hand are electrically neutral before rubbing—that is, each have an equal number of positive and negative charges. After rubbing, the balloon has extra negative charges and the hand is left with extra positive charges. Electric charges follow certain rules, and one rule states that unlike charges are attracted to each other; thus, the negatively charged balloon is attracted to the positively charged hand because of the difference in their charges. Notice in the diagram that there is no change in the total number of combined positive and negative charges on the objects before and after rubbing them together. The rubbing causes the already-present electrons to move from one object to the other.

Let's Explore

1. Does the number of times the balloon is rubbed affect the results? Repeat the experiment twice: first decrease the number of times the balloon is rubbed, and then increase the number of rubbings.
2. Would rubbing the balloon with different materials affect the results? Repeat the original experiment, rubbing the balloon with different types of cloth such as cotton, wool, silk, and/ or rayon and with materials such as paper and plastic. Science Fair Hint: Photographs taken during the testing of the materials, the testing materials themselves, and the results of the test can be used as part of a project display.
3. Does the shape of the balloon affect the results? Repeat the original experiment, replacing the round balloon with a long balloon and/or balloons with wavy shapes.

Show Time!

1. Demonstrate that there is an excess of charge on the area where the balloon is rubbed. Use a marker to put an X on the area of the balloon to be rubbed. Repeat the original experiment, giving the balloon a slight spin to cause it to rotate. The balloon will turn and stop with the X facing your hand.
2. Another way to demonstrate static electricity is to lay about 20 pieces of puffed rice cereal on a table. Wad a 2-foot (60-cm) piece of plastic food wrap to form a piece about the size of your fist. Quickly rub the plastic wrap back and forth across a sheet of paper 10 to 15 times. Immediately hold the plastic above the puffed rice. The plastic should be near, but not touching, the cereal.
3. Clothes removed from a clothes dryer often cling to each other. Prepare a display using simple diagrams or photographs to represent common everyday examples of static electricity.

Check it Out!

Use an encyclopedia, physical science text, and/or other books about electricity to find out more about static electricity. What kind of materials are more likely to be positive? Or negative? How do static charges affect electrical equipment?

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Janice VanCleave's Electricity
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