A changing magnetic field can induce an e.m.f. in a circuit: pushing a bar magnet in or out of a coil or wire causes a current to flow, which can be detected using a galvanometer
The direction of an induced e.m.f. opposes the change causing it: if looking in the direction of the magnetic field, the induced current goes anti-clockwise
The magnitude of induction is directly proportional to the number of coils, the speed of motion and the strength of the magnet
a.c. generator
In a magnetic field, rotating a coil such that the direction of the field, the axis of rotation and the direction of the coil are all perpendicular to one another induces in the coil an alternating current
Each end of the coil are connected to a slip ring, causing the coil to drive the connected circuit with an alternating current
The graph of voltage against number of rotations is a sinusoidal wave