The distribution of a charge over an insulated sphere of conducting material is uniform, provided the sphere is remote from all other conductors and electrified bodies.
Figs. 5 to 8 show, by the dotted lines, the distribution of a charge for bodies of various shapes. Fig. 6 shows that for elongated bodies, the charge collects at the ends.
The effects of points is illustrated in fig. 9; when a charged body is provided with a point as here shown, the current accumulates at the point to such a high degree of density that it passes off into the air, and if a lighted candle be held in front of the point, the flame will be visibly blown aside.
Fig. 10 shows an electric windmill or experimental device for illustrating the escape of electricity from points. It consists of a vane of several pointed wires bent at the tips in the same direction, radiating from a center which rests upon a pivot. When mounted upon the conductor of an electrostatic machine, the vane rotates in a direction opposite that of the points. The movement of the vane is due to the repulsion of the electrified air particles near the points and the electricity on the points themselves. The motion of the air is called electric wind. This device is also called electric flyer, and electric whirl.
“Free” and “Bound” Electricity.—These terms may be defined as follows:
The expression free electricity relates to the ordinary state of electricity upon a charged conductor, not in the presence of a charge of the opposite kind. A free charge will flow away to the earth if a conducting path be provided.
A charge of electricity upon a conductor is said to be bound, when it is attracted by the presence of a neighboring charge of the opposite kind.
Conductors and Insulators.—The term conductors is applied to those bodies which readily allow electricity to flow through them, in distinction from insulators or so-called non-conductors, which practically allow no flow of electricity.