Electromagnetic induction is used in the generation of electricity. The alternating current generator is an electromagnetic devise which transforms mechanical energy into electrical energy.
Simple a.c. generator
Consists of a rectangular coil of wire that is mounted on an axle. By rotating the axle, the rectangle is made to rotate between the poles of a permanent magnet. As the coil rotates the magnetic field through the coil changes and therefore induces an e.m.f. between the ends of the coil. The induced current does not flow unless the ends of the coil are connected to an external circuit with an electrical load such as a resistor. The slip rings permit the transfer of the alternating e.m.f. induced in the rotating coil to the external circuit. Each ring is connected to one end of the coil wire and electrically connected by a conducting carbon brush ( against which it slips) to the rest of the generator circuit.
The slip rings (or commutator) connect the same carbon brush to the same end of the coil so that current can flow to an external load.
To determine the direction of induced current in the coil (Generators)
Factors affecting the magnitude of induced e.m.f.
The induced e.m.f. of the ac generator can be increased by
increasing the speed of rotation of the coil
increasing the number of turns of the coil
winding the coil on a soft iron core
using stronger magnets