A magnet is released along the axis of a copper coil as shown in the diagram.
(a) State the polarity at the top end of the coil when the magnet leaves the coil.
(b) The direction of the current is from A to B when magnet enters the coil. What will be the direction of the current when the magnet leaves the coil.
(c) Name the law which can be used to determine the direction of the induced current in the coil?
(d) State one way to increase the magnitude of the induced current in the coil?
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(a) North pole
Reason — When the magnet leaves the coil, then as per Lenz's law, the bottom end of the coil develops south pole hence top end of the coil develops north pole.
(b) Direction will be from B to A
Reason — When the magnet leaves the coil, then as per Lenz's law, the direction of induced current in the coil will try to oppose it. Hence, it will be in the opposite direction to what it was when the magnet entered the coil. So, direction of induced current will be from B to A.
(c) Lenz's law
(d) Increasing the number of turns in the coil.