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 looks like



Principle of an electric motor

An electric motor works on the principle that

when a rectangular coil is placed in a magnetic field and a current is passed through it,

a force acts on the coil which rotates it continuously


Working of an electric motor

  • When battery is switched on, current flows through coil AB from A to B,
    and Magnetic Field is from North to South...
    So, by Fleming's left hand rule, downward force is applied on AB.

  • Similarly, upward force is applied on CD.
    Thus, the coil rotates with AB moving down and CD moving up

  • Now, as the coil rotates, the rings spin with it
    When coil becomes parallel to the magnetic field,
    the brushes X and Y touch the gap between the rings
    and the circuit breaks


  • And due to inertia, the ring keeps moving... so the opposite end of the ring is now connected the positive end of wire
    Split ring P is connected to coil CD and split ring Q is connected to coil AB.
    Which reverses the direction of current in the circuit.

  • Now, when CD is on left side and AB is on right side..
    Current in CD becomes reversed i.e. from D to C.
    So, force on CD is downwards and force on AB is upwards
    Thus, the coil keeps rotating

  • This reversing of electric current happens every half rotation
    and the coil continues to rotate until the battery is switched off

Function of Split Ring

Function of the split ring is to reverse the flow of current and make coil and axle rotate in the same direction.

Go Ad-free
Maninder Singh's photo - Co-founder, Teachoo

Made by

Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo