(B) Bring them near enough to allow a spark to pass from E C to F B.
EXPERIMENT 100. The human body a frictional electric machine.
Apparatus. Yourself; a carpet; a room with dry air, easily had on a cold winter's day.
215. Directions. (A) Scrape your feet along upon the carpet, then quickly touch your finger to some conductor, as, for example, a friend's nose.
(B) It is possible to light the gas by the above process. Have a friend turn on the gas just before you bring your finger to the jet, and be sure that the spark from your finger passes through the gas on its way to the conductor, the jet.
(C) Bring your finger quickly near a small piece of tissue paper after you have scraped your feet along to charge your body.
216. Static Electric Machines are used to produce large quantities of static electricity. In the early forms, the electrification was produced by friction. Modern machines depend upon the principle of induction. The electrophorus ([Exp. 68]) is really a very simple form of induction machine. The potential of these machines is very great, as the spark may jump many inches. Thousands of Galvanic cells would be needed to make a spark an inch long. When the spark passes through the air it meets with an extremely high resistance, as air practically insulates ordinary electricity. This high resistance in the circuit reduces the strength of the current. While the potential is very high, the strength of the current is very low. (See Ohm's Law.)