1748 – early electroscope

1748 – Jean-Antoine Nollet – Early electroscope

In 1748 Jean-Antoine Nollet built an early electroscope, an electrometer comprised of a suspended pith ball that moves in response to the electrostatic attraction and repulsion of a charged body.

It was a metal box with  isolated wire hung down and a piece of metal foil hanging down.  With a special lense  they amount of movement of the foil could be measured.

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Experiment – Early electroscope

Items needed:

  • Small cardboard box (about 4″x4″)
  • Aluminum foil
  • cork of styrofoam  (to act as a insulator)
  • paperclip
  • balloon
  • hair or wool

The experiment:

  1. Cut a 1/4 inch x 1 inch strip from the aluminum                                                                                                                                                                                     
  2. Cut about a 4 inch square of aluminum foil and roll into a ball
  3. Fold up the aluminum foil, so it is the with of the box.
  4. Cut a hole slightly smaller then the insulator (cork or styrofoam) into the top of the box
  5. Line the box with aluminum foil
  6. Cut a hole in the aluminum foil, where the hole is in the box
  7. Straighten one end of the paperclip
  8. Poke the paperclip through the insulator
  9. Hook the aluminum foil strip onto the hooked end of the paperclip
  10. Put the paperclip and insulator in to the box, with the foil strip on the bottom
  11. Put the ball of foil on the straight end of the paper clip
  12. Rub the balloon on hair or wool
  13. place the charged side of the ballon near the foil ball.
  14. Write down your observations.

Explanation:

As the charge balloon is moved near the foil ball, the electrons in the foil ball are repelled by the negative charge of the balloon.  The foil strip becomes negatively change and is attracted to the neutral charge of the foiled box.

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