Page:Electrical Engineering Volume 1.djvu/25

Rh 2. This charge will be negative at the end A nearest C and positive at the end B farthest from C, as can be shown by an electroscope.

3. The charges at A and B are equal to each other; for if the conductor A B he removed from the vicinity of the conductor C without having touched C, the opposite charges immediately neutralize each other; that is, no electrification will be indicated by the pith-balls.

4. Again, as C is brought nearer and nearer A, the charges of opposite signs on the approaching surfaces attract each other more and more strongly until C is approached very near, and then a spark darts across the intervening space. Two charges rushing together neutralize one another, leaving the induced positive charge, which was formerly repelled to the end B of the conductor, as a permanent charge over all the surface of A B.

5. Or, if the conductor A B be touched by a conductor connected to the earth when it is under the influence of C, the positive charge will neutralize with the earth and the negative charge will remain when A B is removed from the field of C. The charge which passes to the earth from A B is called a free charge, while that charge which is held by the inductive influence of C is a bound charge. Both free and bound charges can be negative or positive, depending upon the sign of the charge on C.

2221. When two conducting bodies, both electrified with equal dissimilar charges, are touched together momentarily, the two charges will neutralize each other, no trace of either remaining; but if they are unequal, the smaller charge will neutralize an equal amount from the larger and leave a charge which is equal to the difference between the two original charges, the sign of the remaining charge being the same as that of the larger one. Before the bodies can be separated, the remaining charge will divide equally between the two bodies. For example, two gilt balls A and B are charged respectively with + 20 and — 4 units of electricity. When the balls are placed in contact, the — 4