Chapter 4: Magnetic Effects of Electric Current

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Magnetic Effects of Electric Current


Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?


Electric Motor: A motor is a device which converts electric energy into mechanical energy.

Principle of Electric Motor: A electric motor works on the principle that a current-carrying conductor placed perpendicular to the magnetic field experiences a force due to which the conductor begins to move, and the electrical energy is converted into mechanical energy.

Split ring (Commutator): It consists of two halves of metallic ring P and Q connected with the end of the armature. The commuter is used to reverse the direction of current in the armature coil.

Working of Motor: When the current flowing through the armature the arm AB and CD experiences a force. By Fleming’s left-hand rule AB experience a downward force and CD experience force in the upward direction. Both the forces are equal and opposite in direction so, the coil starts rotating.

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

When the direction of the current reverses, the direction of force acting on the two arms AB and CD also reverses. Thus, the force on arm AB of the coil now acts in the upward direction whereas the force on arm CD acts in the downward direction.

Again, the coil rotates half a turn more in the same direction.

This reversing of current repeats at each half rotation, giving rise to a continuous rotation of the coil. Hence, the electric energy is converted into mechanical energy.

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