In a reverse of the Motor effect, if we move a wire in a magnetic field then a current will be induced in it. We can use Flemmings Right-hand rule to predict the direction of the current.
NOTE: Of the 3 hand rules you are only expected to know and use the Right Hand Screw Rule and Flemmings Left Hand rule.
If a magnet is moved into a coil of wire which is part of a complete circuit a current is produced (induced) in the wire. If the magnet is moved out of the coil, or the other pole of the magnet is moved into the coil, the direction of the induced current is reversed.
Lenz's Law says that the induced current always opposes the change in the magnetic field which caused it. So if a north pole of a magnet approaches an end of a coil then the coil itself becomes a north pole to try and repel the magnet. If the north pole is then removed the coil will become a south pole to try and attract the magnet. The reverse is true for a south pole. Since we now know what pole the end of a coil becomes we can work out the direction of current required to produce it.
| Will the coil try to repel or attract? | Which pole will the near end of the coil become? | Which direction will the current flow? | |
| North pole into coil | |||
| South pole into coil | |||
| North pole out of coil | |||
| South pole out of coil |