explain the working of electric motor
Answers
Electric motor involve rotating coils of wire which are driven by the magnetic force exerted by a magnetic field on an electric current. The pair of forces creates a turning influence or torque to rotate the coil.
What is electric motor ?
An electric motor is a rotating device that converts electrical energy into mechanical energy. A number of household devices such as fans, mixers, grinders, washing machines etc. consist of a motor.
Do you know how an electric motor works?
Motor principle
The basic principle on which the electric motor works is the magnetic effect of current. A current carrying a rectangular coil starts rotating when placed in a magnetic field. This happens because a continuous magnetic force acts upon it. Rotation of the coil also results in the rotation of the shaft attached to it. Thus, through this process, a motor converts electrical energy into mechanical energy.
Construction of an electric motor
The illustrates the internal parts of a simple electric motor. A motor consists of a rectangular coil MNST of insulated copper wire. The coil is placed between two magnetic poles such that the magnetic field acts normal on lengths MN and ST.
The coil is connected with two carbon brushes at points A and B respectively. The inner sides of these carbon brushes are in contact with half rings C and D, which are insulated and in contact with an axle
Functioning of an electric motor
When a current is allowed to flow through the coil MNST by closing the switch, the coil starts rotating anti-clockwise.Why does this happen?This happens because a downward force acts on length MN and at the same time, an upward force acts on length ST. As a result, the coil rotates anti-clockwise.
The current in length MN flows from M to N, and magnetic field acts from left to right normal to length MN. Hence, according to Flemings left hand rule, a down ward force acts on length MN. Similarly, the current in length ST flows from S to T, and magnetic field acts from left to right normal to its length. Hence, anupward force acts on length ST. These two forces cause the coil MNST and the axle to rotate anti-clockwise.
After half-rotation, the position of length MN and ST get interchanged. Simultaneously, half ring D comes in contact with brush A and half ring C comes in contact with brush B respectively. Hence, the direction of current in coil MNST gets reversed and flows through TSNM.
An electric device that reverses the direction of current in a circuit is called a commutator.
Thus, the split ring acts as a commutator of the electric motor. Now, due to the reverse direction of current in lengths MN and ST, an upward force acts on length MN, which pushes it up and a downward force acts on length ST, which pushes it down. As a result, the coil MNST further rotates anti-clockwise. The reversal of the current through the coil MNST repeats at each half-rotation, while its anti-clockwise rotation continues.
An Commercial moter uses :
- an electromagnet and permanent magnetic poles large number of turns in the rectangular coil
- A core of soft material such as iron on which the coil is wounded. The core becomes an electromagnet when a current flows through the coil.
- The coil core system is known as the armature of motor.
explain the working of electric motor ?
When a current is allowed to flow through the coil MNST by closing the switch, the coil starts rotating anti-clockwise. This happens because a downward force acts on length MN and at the same time, an upward force acts on length ST. As a result, the coil rotates anti-clockwise.
Current in the length MN flows from M to N and the magnetic field acts from left to right, normal to length MN. Therefore, according to Fleming’s left hand rule, a downward force acts on the length MN. Similarly, current in the length ST flows from S to T and the magnetic field acts from left to right, normal to the flow of current. Therefore, an upward force acts on the length ST. These two forces cause the coil to rotate anti-clockwise.
After half a rotation, the position of MN and ST interchange. The half-ring D comes in contact with brush A and half-ring C comes in contact with brush B. Hence, the direction of current in the coil MNST gets reversed
( Refer to the first attachment )
The current flows through the coil in the direction TSNM. The reversal of current through the coil MNST repeats after each half rotation. As a result, the coil rotates unidirectional. The split rings help to reverse the direction of current in the circuit. These are called the commutator.
( Refer to the second attachment )
