Explain the principle of electric generators and the function of brushes

An electric generator is a device that converts mechanical energy into electrical energy.

Principle

It works on Faraday’s law of electromagnetic induction, which states that whenever the magnetic flux through a coil changes with time, an emf (electromotive force) is induced, and this emf produces an electric current in the coil.

Magnetic flux can change in three ways:

1. By changing the strength of the magnetic field.
2. By changing the area of the coil under the field.
3. By changing the orientation of the coil with respect to the field.

Construction

An electric generator consists of:

• A coil of copper wire (armature).
• Strong magnets (horseshoe or cylindrical).
• Split rings.
• Brushes.
• Connecting wires.
• Galvanometer (to detect current).
  The armature is rotated mechanically using energy from diesel, petrol, or other sources.

Working

When the coil (armature) rotates in the magnetic field, the magnetic flux linked with it changes continuously. This induces an emf, which produces current in the coil. The split rings reverse the direction of current after every half rotation, ensuring continuous change in flux and emf. The brushes maintain contact between the rotating coil and external circuit so that the generated current can be transferred outward, where it is detected by the galvanometer.