FIGURE shows a bar magnet, a coil of wire, and a current meter. Is the current through the meter right to left, left to right, or zero for the following circumstances? Explain.

a. The magnet is inserted into the coil.

b. The magnet is held at rest inside the coil.

c. The magnet is withdrawn from the left side of the coil.

a.

A length of rope or wire that has been twisted into a series of loops is known as a coil.

b.

The magnetic field is perpendicular to the wire and in the same direction that your right hand's fingers would curl if you wrapped them around it with your thumb pointing in the current's direction.

(a) From left to right The field inside the coil of the bar magnet points from right to left. The flux passing through the coil is growing. A stream flowing left to right through the meter causes the meter to point left to right.

(b) There is no current flowing through the coil, and the flux through it is not changing.

(c) From right to left As the magnet is withdrawn, the flux across the loop diminishes. Since $B_{\text{original}}$is right to left, $B_{\text{induced}}$is left to right. The right-hand rule causes a current to flow through the meter.