Question

Explain the working of electric motor with a neat diagram?​

Answer 1

1) Consider a rectangular coil kept in uniform magnetic field as shown in below

figure

Switch on the circuit, so that the current flows through the coil. The direction of

current is shown in figure.

2) The sides AB and CD of the coil is always at right angles to the magnetic field.

3) According to Right Hand Rule, at AB the magnetic force acts inwards

perpendicular to the field of magnet and on CD, it acts outward.

4) The top view of coil I shown in figure.

5) The force on the sides BC and DA varies because they make different angles at

different positions of coil in the field. At BC, Magnetic force pulls the coil up and

at DA magnetic force pulls it down.

6) The net force acting on AB and on CD is zero because they carry equal currents

in the opposite directions. Similarly the sum of the forces on sides BC and DA is

also zero. So, net force on coil is zero.

7) But the rectangular coil comes into rotation in clockwise direction because equal

and opposite direction because equal and opposite pair of forces acting on the

two sides of coil.

8) If the direction of current in the coil is unchanged, it rotates, up to half rotation

in one direction and the next half in the direction opposite to previous like to and

fro motion.

9) If the direction of current of coil is changed the coil will rotate continuously in

one and same direction.

10) To achieve these brushes B1 and B2 were used.

11) These brushes are connected to the battery. The ends of coils are connected to

slip rings C1 and C2 which rotate along with coil.

12) Initially C1 is in contact with B1 and C2 is in contact with B2

13) After half rotation, the brushes come into contact with other rings in such a

way that the direction of current through the coil is reversed this happens every

half rotation.

14) Thus the direction of rotation of coil remains the same. This is the principle used

in electric motor.

15) In electric motor electrical energy is converted into mechanical energy.

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