Question

The power of a DC motor can be increased by:
A. increasing the area of the cross section of the coil
B. increasing the current flowing through the coil
C. laminating the soft iron core
D. all of the above

Answer 1

An electric motor is a device which converts electrical energy into mechanical energy. It works on the principle of electromagnetic induction. Example: electric motors are used to pump water to the overhead tanks.

Complete step by step answer:
An electric motor works on the principle of electromagnetic induction that is when a current carrying conductor is placed in a magnetic field, it experiences a force, more specifically torque.
A DC power supply, a magnetic field which is either electromagnets or a permanent magnets, a current conducting coil, a rotor which rotates the coil, a commutator or split rings which reverse the direction of the current in the circuit and axle or brushes which are flexible and conducts electricity between the moving coil and the circuit.
When current flows through the coil which are placed in between the magnets. According to Fleming’s left hand rule, since the current is perpendicular to the magnetic field, the coil experiences a torque, due to which the coil starts to rotate. When the coil completes half the rotation, the DC current gets reversed, causing the torque in the opposite direction. This results in the coil to rotate in the completing the other half cycle in the same direction. This cycle continues.
Clearly, the power of a DC motor depends on the torque of the coil. Since torque depends on the current and the area of the coil. Also, the magnetic field can be increased by adding a soft iron core.

Hence the correct option is D. all of the above.

Note:
The power of a DC motor is the ability of a motor to convert electrical energy into mechanical energy. Since this is due to the principle of electromagnetic induction, we can say that more the torque, more is the power of a DC motor.