Page:Electrical Engineering Volume 1.djvu/149

Rh moved to the right by some exterior means a current is induced in it which tends to flow in an opposite direction to the current which produces the same motion in the former case.

This generation of current may be explained by saying that the motion of the conductor across the lines of force from the magnet sets up an electromotive force in the conductor, which, when the circuit is completed, causes a current to flow. The direction of the current induced in the conductor will be at right angles to the lines of force and to the direction of motion of the conductor.

2442. To determine the direction of induced currents:

Rule.—Place thumb, forefinger, and middle finger of the right hand each at right angles to the other two; if the forefinger shows the direction of the lines of force and the thumb shows the direction of motion of conductor, the middle finger will show the direction of the induced current. (See Fig. 971.)

2443. The positive end of a conductor in which a current is generated by moving across a magnetic field is that end towards which the current tends to flow; the negative end is that from which the current tends to flow.

2444. An electric current will be induced in a coiled conductor when a pole of a magnet is suddenly inserted into the coil. The current will be continuous so long as there is a change in the member of lines of force passing through the