Q. 2 A 4.2( 58 Votes )

Explain the construction and working of the following. Draw a neat diagram and label it.

Electric motor

Answer :

Electric motor- It converts electrical energy into mechanical energy.

Principle- When a current carrying conductor is placed normally in a magnetic field it experiences a force which rotates the conductor thus mechanical energy is generated.


It consists of an armature coil ABCD mounted on an axle. It also consists of two split rings P and Q with brushes X and Y and a horse-shoe electromagnet NS with a dc source.

The rectangular coil is wound around a soft iron core and is placed between two poles of horse-shoe electromagnet. The coil is free to rotate about its axis. The ends A and D are connected to two split rings P and Q which are attached with brushes X and Y respectively. When coil rotates split rings also rotates but brushes remain fixed at their position.


i. When current enters the coil ABCD from battery through brush X and to coil and finally back to brush Y the current flow in coil from A to B upwards and C to D downwards.

ii. So on applying Fleming’s left-hand rule, a force is exerted on arm AB which pushes it downwards and forces on arm CD upwards thus rotating the coil anticlockwise. As both forces are equal and opposite in direction rotating the coil.

iii. After half rotation split, ring P contact with brush Y and split ring Q contact with brush X thus current will flow in DCBA path.

iv. Now force acting on both arms of the coil will be reversed and coil will continue to rotate according to Fleming’s left-hand rule and complete the next half turn in the same direction. Thus the coil rotates continuously.

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