Question

at what principle does the electric motor work draw it diagram also

Answer 1

Electric motor: A motor is a device which converts electrical energy into mechanical energy.
Principle of motor : A motor works on the principle that when a rectangular coil is placed in a magnetic field and current is passed through it. A force acts on the coil which rotates it continuously.

When electric current is passed into the rectangular coil, this current produces a magnetic field around the coil.The magnetic field of horse shoe-type magnet then interacts with the magnetic field of the coil and causes the coil to rotate continuously.If ABCD is in horizontal position current from battery enters the coil through brush $B _{ 1 }$, and commutator half ring C:. The current flows in the direction ABCD
and leaves via ring and brush $B _{ 2 }$The direction of current is from A to B, the direction of current is from C to D. The force on side AB of the coil is in the downward direction. Whereas the force on the side CD of the coil is in the upward direction. ABCD rotate in anti-clockwise direction.While rotating when the coil reaches vertical position then the brushes $B _{ 1 }$ and $B _{ 2 }$ will touch the gap between the commutator rings and current to the coil is cut off. But the coil does not stop rotating because it has already gained momentum.The coil CD comes on the left side and AB comes to the right side. Again they come in contact with brush $B _{ 1 }$ Current direction is reversed.The reversing of current in the coil is repeated after every half rotation due to which the coil continue to rotate as long as current from the batter is passed through it. The rotating shaft of electric motor can drive a large number of machines which are connected to it.

Answer 2

it works on principal of Fleming left hand rule for diagram see ncert page no 232