What we did: static electricity experiments

  1. Rubbed rods of various materials (PVC, acrylic, glass, delrin, etc.) with different kinds of cloth (fur, plastic, felt, fabric, etc.) and used the then negatively-charged rods to pick up small bits of paper.
  2. Observed and used a Wimshurst machine (What’s a Wimshurst machine?)
  3. Rubbed an ebonite rod and and another suspended ebonite rod with a furry material and tried to use the rods to repel each other.
  4. Rubbed an ebonite rod with a furry material and used it to repel a pith ball electroscope (What’s an electroscope?)
  5. Rubbed an ebonite rod with a furry material and used it to set off a gold-foil electroscope
  6. Used a Van de Graaff electrostatic generator to repel small bits of paper.

So, how did it work?

Oppositely charged objects (positive with negative) or charged and neutral objects (positive/negative with neutral) attract. This is the law of electric charges. When two objects come into contact, such as rubbing to generate friction, the electrons may move from one object to another, given that the objects are made of different materials.

  1. This experiment worked by rubbing the rods with various materials to make the rods negatively charged. Since negatively charged objects (in this case, the rod), and neutrally charged objects (in this case, the paper) attract, the rod was able to pick up the pieces of paper like a magnet.
  2. When the wheels of the machine turned, other parts of the machine rubbed against each other to generate a spark via the friction generated. The Wikipedia article describes the phenomenon pretty well:

    In a Wimshurst machine, the two insulated discs and their metal sectors rotate in opposite directions passing the crossed metal neutralizer bars and their brushes. An imbalance of charges is induced, amplified, and collected by two pairs of metal combs with points placed near the surfaces of each disk. These collectors are mounted on insulating supports and connected to the output terminals. The positive feedback increases the accumulating charges exponentially until the dielectric breakdown voltage of the air is reached and an electric spark jumps across the gap.