1742 – Electrostatic Bells

1742 – Electrostatic Bells – Andrew Gordon

About 1742 Andrew Gordon, a Professor of Natural Philosophy at the University at Erfurt in Germany, invented the Electrostatic Bells. It was the first invention to convert electrical energy into mechanical energy. Benjamin Franklin later used this invention to detect lighting storms and they became more commonly known as “Franklin Bells”.

Experiment – Electrostatic Bells

Items needed:

  • 2 metal cans cleaned and labels removed
  • non-conductive threads, like cotton or silk
  • paperclip or pop tab
  • pencil or stick
  • wire
  • water faucet
  • Plastic cling wrap
  • Wool
  • Non-conductive surface like a counter top or styrofoam.

The experiment:

  1. Place the cans neat a water fauset and about 1/2 inch apart on the non-conductive surface or styrofoam.
  2. Take the wire and make sure both end are exposed and can conduct electricity. (stripe the plastic off both ends or scrap the protective layer off the end of the wire.
  3. Tape one end of the wire to the one of the cans and tape the other end to the metal part or a faucet.  Some faucets contain a non-conductive coating at will hamper the cunduction of electricity.
  4. Tie one end of the thread to a paperclip.
  5. Place the other end to the middle of the pencil or stick so that the paperclip or pop tab and thread are about 1/2 inch short than the cans
  6. Place the pencil on top of the cans, such that the thread hangs in the middle of the space between the cans.
  7. lay the plastic wrap on a surface and rub  it vigrously with the wool
  8. Once a large static charge has build up on the plastic wrap, with both hands pick up the plastic wrap by one edge.
  9. Care bring it to the can without the wire to the faucet, without touching the can, place teh plastic on the can, so it partially wraps around the can.
  10. Write down your observations.
  11. Once the paperclip stops moving.  pull the plastic wrap off the can.
  12. Write down your observations.

Explanation:

The short explanation is: Rubbing the wool on the plastic wrap builds up a charge.  The change is then transfered to the can.  Since the can is conductive, meaning the electrons can move, the charge is dispursed on the can. The charge on the can repells the charge on the one side of the paperclip, makiong the near side of the paperclip the opposite charge.  Since opsosites attract, teh paperclip is attracted tio the charged can.  When the paperclip touches the can it becomes charged and is repelled from charged can and attracted to the grounded can (the one attached to the water faucet).  When it touches the grounded can, it gives up it’s change and become nuetral and is attacted the changed can.  This repeats, until the charge is almost neutral.  Then when you remove the plastic wrap, it causes the can to be charged in the opposite direction and the whole thing happens again.

 

The longer explanation: The can connected to the faucet is neutral, because any excess electrons will flow to the water faucet. This is called grounded.

When the plastic wrap is rubbed, it receives electron from the wool and become negively charged. The other side becomes postively changed.  This is because the negively side repells the electrons on the opposite side and makes the surface is it laying take some  the electrons.

When you place the plastic wrap on the can, the can becomes charged.  This causes the paperclips to have a unbalanced charge on each side of it.   This imbalance causes the opposite charge sides to attract each other.  When they touch the paperclips becomes more positive or negitive and is repelled from the can. 

Since there is a charge difference between the paperclip and the can, the paperclip is attracted to the grouned can (the one with a wire attached).  Once is touches the grounded can, it becomes evenly balance (by giving up or getting electrons).   Now the can it neutral, it is no longer attracted to the can with the wire and it falls back toward the middle, where it’s charges become imbalanced on each side of it and is attracted to the can with the plastic wrap and the whole cycle begins again.  Until the charge on the can with the static wrap becomes to weak to attract the paperclip and stopped.

The is until the plastic wrap is removed.  When the plastic wrap is removed the side not touching the can has positive side charged and when the wrap is  pulled off the wrap takes some electron with it, because they are attracted to the positive side and the paperclips bounces back and forth between the cans, until the charge on the can is almost neutral.

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