Construction: There are four main parts in an AC generator, viz. field magnet, armature, slip ring and brushes.
Field Magnet: This is a very powerful magnet; as shown by NS in given figure.
Armature: This is composed of a rectangular coil ABCD which has insulated copper wire wound around a frame of cast iron.
Slip Ring: Two metallic rings S1 and S2 are connected respectively to the ends A and D of coil. These rings rotate along with rotation of coil.
Brushes: These are made of carbon or any metal. One end of brushes touches the slip ring while another end touches other part of the circuit.
Working of AC Generator: When armature moves then magnetic flux through ABCD changes continuously. This induces current at the ends of the coil. When coil is rotated clockwise then the plane of coil keeps on alternatively becoming perpendicular and parallel to the magnetic field.
As magnetic flux reduces in first half cycle, the direction of current is clockwise in external circuit during the first half cycle. This means that during the first half cycle, current moves from B1 to B2. In the next half cycle, current moves from B2 to B1 Thus, direction of current keeps on changing after every half cycle of the armature. “When direction of current keeps on changing, it is called alternating current or AC Current.”
