Question

Draw a labelled diagram of an electric motor. Explain its principle and parts.

Draw a diagram of an electric motor and explain its structure and function.

Answer 1

                         Simple DC motor

Principle of a DC motor:

When an electric current is passed through a rectangular coil placed in a magnetic field, the coil experiences a mechanical force that rotates it continuously. The direction of this motion is determined using Fleming's Left-Hand Rule.

Construction and Parts:

• Armature Coil (ABCD): It is a rectangular coil of insulated copper wire wound around a soft iron core. It is mounted on a shaft and can rotate freely between the curved poles (N and S) of a powerful electromagnet.
• Commutator (Split Rings S₁ and S₂): It consists of a copper ring split into two halves (S₁ and S₂) that are insulated from each other and fixed onto the shaft. The two ends (A and D) of the coil are permanently connected to these rings, causing them to rotate alongside the coil. Its function is to reverse the direction of current in the coil after every half-rotation.
• Carbon Brushes (B₁ and B₂): These are stationary carbon strips fixed to the motor base that press lightly against the rotating split rings. They act as sliding contacts to pass electricity from the battery into the rotating coil without twisting the connecting wires.
• Power Source (Battery): A DC battery is connected across the carbon brushes through a switch to supply the required electric current to the armature coil.