Question

Explain the principle and construction of an AC generator. Draw its diagram and clearly label the parts.

Answer 1

Principle:

An AC generator works on the principle of electromagnetic induction. When a rectangular armature coil is rotated continuously inside a strong magnetic field, the magnetic flux linked with the coil changes continuously. This changing magnetic flux induces an electromotive force (emf) and an alternating current across the ends of the coil.

Construction:

• Armature Coil: A large rectangular loop of insulated copper wire containing a large number of turns wound over a soft iron core.
• Field Magnets: Strong concave permanent magnetic poles (North and South) that provide a strong magnetic field perpendicular to the axis of the coil.
• Slip Rings: Two full continuous copper rings (R₁ and R₂) mounted on the central shaft that rotate along with the armature coil.
• Carbon Brushes: Two stationary flexible carbon strips (B₁ and B₂) that press lightly against the rotating slip rings to maintain electrical contact with the external circuit.
• External Circuit: A closed loop containing a load or galvanometer connected across the stationary brushes to utilize the generated alternating current.