Sticky-Tape Electroscope

Emmette Cox
Project Management Coordinator, Physical Science

September 2015

Static electricity. It’s fascinating. We’ve all experienced it. We know that an incredible amount of power occurs in the static discharge of a lightning bolt. Such 18th-century scientists as Ben Franklin and John Carl Wilcke, who studied static electricity and the new quantity “charge,” laid the foundation for later scientists to explore electric current and develop the technologies that now define our modern age, including power stations, electric lights, radio, TV, and telephones. Students need to understand the concepts involved in static electricity, yet science class typically includes few demonstrations of it. Turn your next lesson on static electricity into a lesson on the scientific method with this activity. All you need is tape plus a few other items from home or classroom (perhaps found in a basic static electricity kit).

A simple electroscope

Somewhere in your class or equipment room you probably have an electroscope. This simple device consists of a metal rod with 2 metal foil leaves at 1 end. It most likely has a glass case or is built into a flask. When you bring a charged object near the electroscope, the leaves separate due to an induced charge. Create a similar device with nothing more than 2 pieces of clear adhesive tape.

Safety

This activity is fairly safe; however, some experiments with electricity can generate large, dangerous voltages. It is not recommended to use this activity with equipment that generates or stores large amounts of electrical charge.

Materials

• Clear Adhesive Tape
• Rubber Balloon
• Wool
• Foam Cup
• Nylon Rod
• Vinyl Sheet

Procedure 1

Two pieces of tape with a like charge repel each other.

1. Cut 2 pieces of clear adhesive tape, each about 10 cm long.
2. Fold 1 end of each piece of tape about 2 cm from the end, allowing you to hold the tape without sticking to it.
3. Attach each piece of tape to the top of a desk or lab table so the end with the “handle” hangs over the edge (see Fig. 1).
4. Pull both pieces of tape from the table.
5. Hold the 2 pieces of tape so the non-stick sides face each other, and bring the 2 pieces of tape near each other (see Fig. 2).

Procedure 2

Two pieces of tape with a different charge attract each other.

1. Label the non-sticky side of the 2 pieces of tape as “1” and “2,” “A” and “B,” “Top” and “Bottom,” or any other name you want to give them, just so long as you can tell them apart.
2. Place 1 piece of tape on the table, sticky side down, exactly as before.
3. Place the second piece of tape directly on top of the first (see Fig. 3).
4. Pull both pieces of tape off the table so they remain stuck together.
5. Pull the 2 pieces of tape apart.
6. Hold the 2 pieces of tape so the non-adhesive sides face each other, and bring the 2 pieces of tape near each other (see Fig. 4).

Procedure 3

A charged object will attract 1 piece of tape and repel the other.

1. After you complete Procedure 2, attach each piece of tape to the edge of the table so that each piece hangs down toward the floor. Make sure the “handle” you made when you folded the tape is at the top, and place the 2 pieces of tape several inches apart from each other (see Fig. 5).
2. Bring a charged object near each piece of tape. Some good choices are an inflated rubber balloon that you have rubbed on your hair or a nylon rod that you have rubbed with a piece of vinyl sheeting.

Explanation

When both pieces of tape are pulled off the same table, they both pick up the same type of charge, but when the pieces of tape are pulled off the table together, then separated, they pick up an opposite charge. When you hang the pieces of tape from a table and bring a charged object near the 2 pieces of tape with different charges, 1 piece of tape is attracted to the object and the other is repelled.

Troubleshooting

Static electricity experiments work better with less humidity. Also, the tape may lose charge on its own or if it touches 1 of the charged objects. This experiment works best in dry conditions, and you may have to repeat Procedure 2 to re-charge the tape.

Laboratory discussion question

Charge is a property of matter, like mass or volume. A buildup of charge on 1 object is called static electricity. When 2 objects made from different materials are rubbed together, sometimes charge is transferred—1 object becomes positively charged and the other object becomes negatively charged. This is called the triboelectric effect. In 1757, John Carl Wilcke published a list called the triboelectric series that identified which materials gained a positive charge and which gained a negative charge. Try using the oppositely charged pieces of tape from procedure 2 and repeating procedure 3 with different materials to create a list of materials with like and opposite charges. According to the triboelectric series, a foam cup rubbed with wool picks up a negative charge, and nylon rubbed with vinyl picks up a positive charge. Can you use the sticky-tape electroscope to verify which objects have like and opposite charges? What other materials can you test?