Electroscope

Objective: Build a homemade electroscope, a device that detects electrical charge.

Materials: 4 Plastic Soda Straws with flexible ends

2 plastic 35-mm film cans

Modeling Clay (enough to fill cans halfway)

One Roll of Scotch Tape

Plastic Comb or Wool Sock

Demonstration:

1) Press enough modeling clay into both film cans to fill them halfway.

2) Press inflexible ends of two soda straws into the clan in each can.

  • 3) Bend the flexible ends to form horizontal arms that extend in opposite directions. Height of straws should be the same.
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    • 4) Tear off two 4" pieces of tape.

  • 5) Press them firmly onto the table and rip them off. Place one tape on one straw in the first can and the other on another straw in the second can.
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    • 6) Move the two cans closer together and observer what happens.

  • 7) Tear off two more pieces of tape and place the sticky side of one onto the smooth side of the other. Quickly rip them apart and place one on the other straw in the first can and the other on the other straw in the second can.
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    • 8) Move the two cans closer together and observer what happens.

    9) Run the comb through your hair, and place near tapes. Observer what happens.

     

    Discussion:

    As you notice, the tapes that were both pulled from the table both repel each other. This is because they both have the same charge, and like charges repel. When the two tapes that were pulled off from the smooth side of one another are put close together, they attract. This is because they have opposite charges and opposite charge attracts. When you place the comb near the tapes, it will repel the tape that was pulled from the table because they have the same charge. And it will attract the tape whose smooth side was in the middle of the sandwich.

     

    Extension:

    You can also show the effects of static electricity by rubbing balloons on the top of your head or on a sweater. Then when it is charged up put it on top of someone else’s head, observe what happens. It should attract the other person’s hair.

    Pictures Needed:

    Take Picture from the Exploratorium Science Snackbook.