A potential difference can be induced if an electrical conductor moves across a magnetic field or if there is a change in the magnetic field around a conductor. This is known as electromagnetic induction, which is the opposite of the motor effect because we are generating electricity from motion.
Electromagnetic induction works if there is relative movement between the electrical conductor and the magnetic field. For example, if the conductor is a coil of wire, we can:
In both cases, the magnetic field around the coil of wire changes when the coil cuts through the magnetic field. If the magnet is moved back and forth through the coil, the direction of current changes, which creates an alternating current.
If the conductor is part of a complete circuit, a current will be induced. This induced current will generate a magnetic field that will oppose the change (e.g. the movement of the conductor or the change in magnetic field).
The direction of induced potential difference depends on the magnet’s movement. The direction can be reversed by:
The induced potential difference can be increased by: