Draw a labelled circuit diagram of a simple electric motor and explain its working. In what way these simple electric motors are different from commercial motors?

Working of Electric Motor:-

An electric motor is a rotating device which converts electrical energy into the mechanical energy.

Construction of an electric motor:

An electric motor consists of a rectangular coil of insulated wire. The rectangular coil is placed between the two poles of magnetic field such that the arm AB and CD are perpendicular to the direction of the magnetic field. The ends of the coil are connected through two halves of a split ring. The inner sides of the halves are insulated and attached to an axle. The external edges of the conducting halves touch two conducting stationary brushes X and Y.

Working of an electric motor:

Current flowing in the rectangular coil ABCD from the battery source through conducting brush X and the current flows back to the rectangular coil through brush Y. The current in arm AB of the coil flows from A to B and in arm CD, it flows from C to D i.e. opposite to the direction of the arm AB. The direction of current can be find out using Fleming’s left hand rule. The force acting on arm AB pushes it downwards and while force acting on CD pushes it downwards. Therefore, the coil and the axle are free to turn about an axis and can rotate in anticlockwise direction. At half rotation, Q makes contact with brush X and P with brush Y. So, now the current is reversed and flows along the path DCBA. The split ring acts as a commutator in the electric motor. On reversing the current, the direction of force acting on arms AB and CD also gets reversed. Now AB will be pushed in upward direction and CD will be pushed in downward direction. So, now the coil and axle rotate a half turn more in the same direction. The current reverses in every half rotation of the coil to the axle.

Commercial electric motors don’t use a permanent magnet to rotate the armature instead commercial electric motors uses an electromagnet for rotating the armature.