Question

how does electric motor work

Answer 1

The basic idea of an electric motor is really simple: you put electricity into it at one end and an axle (metal rod) rotates at the other end giving you the power to drive a machine of some kind. How does this work in practice? Exactly how do your convert electricity into movement? To find the answer to that, we have to go back in time almost 200 years.

Suppose you take a length of ordinary wire, make it into a big loop, and lay it between the poles of a powerful, permanent horseshoe magnet. Now if you connect the two ends of the wire to a battery, the wire will jump up briefly. It's amazing when you see this for the first time. It's just like magic! But there's a perfectly scientific explanation. When an electric current starts to creep along a wire, it creates a magnetic field all around it. If you place the wire near a permanent magnet, this temporary magnetic field interacts with the permanent magnet's field. You'll know that two magnets placed near one another either attract or repel. In the same way, the temporary magnetism around the wire attracts or repels the permanent magnetism from the magnet, and that's what causes the wire to jump.

Fleming's Left-Hand Rule



You can figure out the direction in which the wire will jump using a handy mnemonic (memory aid) called Fleming's Left-Hand Rule(sometimes  called the Motor Rule).

Hold out the thumb, first finger, and second finger of your left hand so all three are at right angles. If you point the seCond finger in the direction of the Current (which flows from the positive to the negative terminal of the battery), and the First finger in the direction of the Field (which flows from the North to the South pole of the magnet), your thuMb will show the direction in which the wireMoves. 

That's...

First finger = Field
SeCond finger = Current
ThuMb = Motion

Answer 2

Here is the answer

The given attachment shows the construction of an electric motor.

Structure: 

Here, 
A rectangular loop ABCD of copper wire with resistive coating is placed between the North Pole and South Pole of a strong magnet { Horseshoe magnet } such that the branches AB and CD are perpendicular to the direction of the magnetic field. 

The ends of the loop are connected to the two halves , X and Y , of split rings - X and Y have resistive coating on their inner surfaces and are tightly fitted to the axle.
The outer conducting surfaces of X and Y are in contact with the two stationary brushes , E and F , respectively.

Working: 
When the circuit is completed with the plug key or switch the current flows in the direction 
E ➡️A➡️B➡️C➡️D➡️ F.

As the magnetic field is directed from the north pole to the South Pole the force on AB is downward and that on CD is upward by the Fleming's Left Hand Rule. Hence , AB moves downward and CD upward.

These forces are equal in magnitude and opposite in direction, Therefore, As observed from the side AD , the loop ABCD and the axle start rotating in anticlockwise direction.

After half rotation, X and Y come in contact with brushes F and E respectively and the current flows in direction E-D-C-B-A-F.
Hence, the force on CD is downward and that on AB is upward.Therefore , the loop and the axle continue to rotate in the anticlockwise dierection.

After every half rotation, the current in the loop is reversed and the loop and the axle start rotating in the anticlockwise direction.

When the current is switched off, the loop stops rotating after some time.