Question

An electric motor works on the principle
A. of electromagnetic induction
B. 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.
C. both A and B
D. None of the above

Answer 1

Hint: Recall the working process of an electric motor. Check the options given for the principle of working of the electric motor. Go through the working of an electric motor and guess what should be the basic principle related with its working.

Complete answer:
The principle of electromagnetic induction states that when a current carrying conductor is placed in a varying magnetic field, the changing flux induces the electromotive force in the conductor which in turn produces an electric current. Hence, using the principle of electromagnetic induction an electric current is produced in the conductor. This is not the basic principle on which an electric motor works. Hence, the option A is incorrect.

In an electric motor, a rectangular coil is placed between two strong magnets. When an electric current is passed through this rectangular coil, a force acts on the coil and torque is produced. This torque produces the rotational motion in the coil and the rectangular coil rotates continuously until an electric current passes through it.

Therefore, an electric 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.

Hence, the correct option is B.

Note:One may get confused between the basic principle of working of electric motors and generators. The principle of electromagnetic induction is used in generators which converts mechanical energy into electrical energy. But in electric motors, the electrical energy is converted into mechanical energy using principle given in option B.