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How to Create Negative Polarity

When you walk across a carpeted floor in winter and touch a metal doorknob, you get a small shock from static electricity. Friction from the rubber soles of your shoes against the carpet fibers builds up positive electric charges in the rug and negative charges in your body. A list of different materials, called the triboelectric series, shows which materials end up with a negative polarity when rubbed and which become positive. The material with the higher relative position becomes positive and the other becomes negative.

Things You'll Need

Wool cloth
Hard rubber rod
Empty soft drink can

Instructions

- 1
  Wrap the wool cloth around the rubber rod and rub the cloth vigorously on the rod. You will hear a crackle of static electricity as charges build up on both. The rod receives negative charges; the cloth becomes positive.
- 2
  Lay the soft drink can on its side on a flat surface. Bring the rod to within a few inches of the can without touching it. The can should roll toward the rod, as the negatively-charged rod attracts positive charges in the can.
- 3
  Transfer some of the negative charges to the can by stroking the can with the rod. Rub the rod with the cloth again to put more negative charges onto the rod. Bring the rod close to the can. Now the can should roll away from the rod. The rod's negative charges repel the can's negative charges. Opposite charges attract; like charges repel.

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