Electric Motor : Principle, Construction, Working and Uses

Electric Motor

Electric Motor:-

An electric motor is a rotating device that converts electrical energy to mechanical energy.


It is based on the principle that when a current carrying conductor is placed in a magnetic field perpendicular to it, it experiences a force.


Consider a rectangular coil ABCD placed in a magnetic field such that AB and CD are perpendicular to the direction of magnetic field. The ends of coil are connected to two halves split rings. The inner sides of split rings are insulated and attached to an axle. The external conducting edges of split rings touch two carbon brushes. The opposite sides of brushes are connected with battery and key as shown in figure.

Fig: DC Motor

Commutator:- A device that reverses the direction of flow of current through a circuit is called a commutator.

 In electric motor, split rings act as commutator.

Armature:- The soft iron core, on which the coil is wound, plus the coils is called an armature.


According to the figure, the current in the coil ABCD enters from brush X. Since current carrying coil ABCD is placed in a magnetic field perpendicular to it. So by Fleming’s left hand rule, we can say that AB moves in downward and CD moves in upward direction. In next half rotation, CD comes towards north pole and AB comes towards south pole. Again by applying Fleming’s left hand rule, we see that AB moves in upward and CD moves in downward direction. This process continues and the coil starts rotating.

Source: Uniclass Content

In commercial motors,

  • an electromagnet is used in place of permanent magnet.
  • large number of turns of coil is used.
  • a soft iron core is used on which the coil is wound.

Uses of Electric Motor:-

It is used in electric fans, refrigerator, mp3 player, washing machine etc.

 DC motor consists of split rings while AC motor consists of two slip rings.


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