Question

Explain the principle and working of an electric motor with detailed diagram

Answer 1

Answer:

$\huge\bold\star\</strong><strong>r</strong><strong>e</strong><strong>d</strong><strong>{Answer}\star$

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

Answer 2

Answer:

Electric motor works on principal of converting electrical energy to mechanical energy.

Construction :

1) Electric motor consists of a rectangular coil ABCD of insulated copper wire.

2) The coil is placed between the two poles of a permanent magnet such that the arms AB and CD are perpendicular to the direction of the magnetic field.

3) The ends of the coil are connected to

two halves P and of a split ring.

4) The inner sides of these halves are insulated and attached to an axle such that they can rotate easily on it.

5) The external conducting edges of P and Q touch two conducting stationary brushes (i.e.. carbon strips) X and Y respectively.

6) These brushes are connected to a plug key and battery as shown in figure 13.24.

Working :

1) Current in coil ABCD enters from the source-battery through conducting brush X and flows back to the battery through brush Y.

2) Current in arm AB of the coil flows from A to B while in arm CD it flows from C to D. i.e.. opposite to the direction of the current through AB. Both the currents flowing in AB and CD are perpendicular to the magnetic field.

3) On applying Fleming's left hand rule for finding the direction of the force on a current carrying conductor in a magnetic field (see figure 13.24), we find that the force acting or arm AB pushes it downwards while the force acting on arm CD pushes it upwards. These forces are also equal in magnitude and perpendicular to the respective lengths of arms AB and CD.

4) So. the coil and the axle, mounted free to turn about an axis, rotate anticlockwise.

5) At half rotation, Q makes contact with brush X and P with brush Y. Therefore, the current in the coil gets reversed and flows along the path DCBA.

6) A device that reverses the direction of flow of current through a circuit is called a commutator.

In an electric motor the split rings act as a commutator.

7) Now, the reversal of current also reverses the direction of the force acting on the arms AB and CD. Thus arm AB that was earlier pushed down, is now pushed up and arm CD previously pushed up. is now pushed down.

8) Therefore, the coil and the axle rotate half a turn more in the same direction..

9) The reversing of the current is repeated at each half rotation, giving rise to a continuous rotation of the coil and the axle.

Important note: When currents through arms BC and DA are either parallel or antiparallel to the magnetic field. magnetic force does not act

on them.