Chapter 4: Magnetic Effects of Electric Current

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Magnetic Effects of Electric Current


Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of the brushes?


Electric Generator:  An electric generator is a device which converts mechanical energy into electrical energy.

Principle of Generator: An electric generator works on the principle of electromagnetic induction and Fleming’s right-hand rule.

Working: When the axle attached to the two slip rings is rotated in such a way that the arm AB moves up and the arm CD moves down in the magnetic field, that is, in the clockwise direction then the current is induced in arms AB and CD. By applying Fleming’s right-hand rule, the direction of induced current in arm AB is from A to B and in CD from C to D. So, it flows along is ABCD. The induced current flows in the circuit through X to Y.

After half a rotation, arm AB starts moving downward and arm CD moves upward. As a result, the directions of the induced currents in both the arms change, resulting in an induced current in the direction DCBA. The induced current flows in the circuit through Y to X.

Therefore, after every half rotation the direction of current in each arm changes. The current which changes its direction after an equal interval of time is called alternating current.

This type of generator is called A.C. Generator.

Brushes: Two carbon brushes are connected with the slip rings. Brushes in contact with rings provide the current for external use.

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