Question

In a DC generator, the induced e.m.f in the armature is:
A. DC
B. AC
C. Fluctuating DC
D. Both AC and DC

Answer 1

Hint: The induced e.m.f in the armature of a DC generator varies with time. We can also say that it reverses with time. We use the split ring in the generator which acts as a commutator.

Complete answer:
To begin with, we need to discuss the generator and its working principle in a brief way, to help one to understand better. A generator is a device which converts the mechanical energy to electrical energy. It is simply the reverse of an electric motor.

A rectangular coil is put in an electric generator between the magnetic field and as AC current flows from the split ring commutator through the coil, a torque works on the coil that constantly rotates it. The split ring mechanism is used to reverse the current at that point to preserve the direction of the current in the external circuit to travel in the same direction as DC current to prevent the torque from reversing any time the coil passes across the plane perpendicular to the magnetic field in compliance with Fleming's right-hand thumb law. The split ring commutator consists of two bits of copper that are held separate from touching each other in the middle. In the centre, they appear like a copper ring broken. It is thus called the split ring commutator.

Hence, we can come to the conclusion that in a DC generator, the induced e.m.f in the armature is purely AC. The correct option is B.

Note:Defined as AC (alternating current) and DC (direct current) generators, there are two basic types of generators. In both forms, though the procedure of generating electricity is the same, AC and DC power differ in terms of their applications and the way electricity is generated by loads.