Page:Electricity (1912) Kapp.djvu/174



the previous chapter it was shown that a wire placed in a magnetic field will, when traversed by a current, be subject to a force tending to displace it in a direction which is at right angles both to the axis of the wire and to the direction of the lines of force. An easy way for finding in each case in which direction motion will be produced is to use the left hand for indicating the three quantities concerned, namely, direction of the magnetic force, current and motion. Set thumb, forefinger and middle finger at right angles to each other, and place the hand so that the forefinger points in the direction of the lines of force, and the central finger in the direction in which the current flows, then the thumb will indicate in which direction the wire will tend to displace itself.

If the displacement is allowed to take place,