Page:Electrical Engineering Volume 1.djvu/30

 charge and the other with a negative charge, the two charges will attract one another, or, in other words, they are held or bound by each other. It will be found that these two pieces of tin-foil may be charged a great deal stronger in this manner than either of them could possibly be if they were stuck to the glass alone and then electrified. This property of retaining and accumulating a large quantity of static charges which two conductors possess when placed side by side and separated from each other by a non-conductor, is called their capacity.

2231. A condenser is an apparatus for condensing or accumulating a large quantity of static charges of electricity on a comparatively small surface, and consists of two conductors separated by a thin layer of some non-conducting material. One of the plates is entirely insulated from the earth, and the other is connected to it by a conductor.

The capacity of a condenser depends upon (1) the size and form of the condensing plates, (2) the thinness of the insulating material between them, and (3) the inductive capacity of the insulating material.

2232. A convenient form of condenser is called the Leyden jar, Fig. 907. It consists of a glass jar J coated

up to a certain height on the inside and outside with tin> foil. A brass knob a is fixed on the end of a stout brass wire, which passes downwards through a lid or stopper of dry, well-varnished wood, and connected by a loose bit of brass chain with the inner coating of the jar.