Posted on 4th Sep 2021 05:47:38 in
Question 16) Explain the underlying principle and working of an electric generator by drawing labelled diagram. What is the function of brushes?
Principle of Electric Generator
Electric Generator operates on the principle of electromagnetic induction.When an coil is rotated in magnetic field, an induced current is produced in the circuit and direction of induced current is given by Fleming’s right hand rule. Electric generator converts mechanical energy into electrical energy.
Working of electric Generator
a. When the coil ABCD is rotated clockwise . By applying Flemings right-hand rule, the induced currents are set up in these arms along the directions AB and CD. Thus an induced current flows in the direction ABCD. This means that the current in the external circuit flows from B2 to B1.
b. After half a rotation, arm CD starts moving up and AB moving down. As a result, the directions of the induced currents in both the arms change, giving rise to the net induced current in the direction DCBA. The current in the external circuit now flows from B1 to B2. Thus after every half rotation the polarity of the current in the respective arms changes. Such a current, which changes direction after equal intervals of time, is called an alternating current (abbreviated as AC). This device is called an AC generator.
c. To get a direct current (DC, which does not change its direction with time), a split-ring type commutator must be used. With this arrangement, one brush is at all times in contact with the arm moving up in the field, while the other is in contact with the arm moving down. Thus a unidirectional current is produced. The generator is thus called a DC generator.
