Question

Draw a labelled circuit diagram of an electric generator and explain its principle and working.

Hint:

AC Generator: Uses slip rings → alternating current.
DC Generator: Uses split-ring commutator → direct current.

Answer 1

Principle:
The working of an electric generator is based on
Faraday’s law of electromagnetic induction, which states that: \[ \text{Whenever magnetic flux linked with a coil changes, an electromotive force (emf) is induced in the coil.} \] The direction of the induced current is given by
Fleming’s right-hand rule.

Construction:
An electric generator consists of:

• A rectangular coil (armature) \( ABCD \) mounted on a rotating shaft between the poles of a strong magnet.
• Two slip rings \( R_1 \) and \( R_2 \) connected to the ends of the coil.
• Two brushes \( B_1 \) and \( B_2 \) that maintain contact with the slip rings and connect to an external circuit or load.

Working:
When the armature coil rotates in the magnetic field, the magnetic flux linked with the coil changes continuously. Due to this change in flux, an
induced emf is generated in the coil. The current thus produced flows through the external circuit via brushes.

The direction of current reverses after every half rotation, so the generator produces an
alternating current (AC).

\[ \text{e} = -\frac{d\phi}{dt} \] where \( e \) = induced emf and \( \phi \) = magnetic flux.

For DC Generator:
If the slip rings are replaced by a
split-ring commutator, the current direction in the external circuit remains the same, producing
direct current (DC).