Question

what is working principle of DC motor

Answer 1

1. Like poles of a magnet repel and unlike ones attract. All of us has played with magnets and we do know this simple observation.

2. Magnetic effect of current.


A dc motor has two magnetic fields, one produced by the field or stator. It can be a permanent magnet or an electromagnet. Usually smaller dc motors use permanent magnets.

The second magnetic field is produced by the rotor / armature / many other names. This is the rotating part. It is always of electromagnet type and consists of insulated wire around a soft iron core.

Now when current is passed through the armature it behaves like an electromagnet and a force is exerted on the armature due to the magnetic field by the stator. Now the situation is quite similar like two magnets brought close together to each other - they will either repel each other or attract. The armature is constructed in such a way that one of its side is attracted and the other is repelled and this causes it to rotate.

Such an armature can make only half a rotation cause the sides of the armature gets reversed and so as the magnetic forces acting on them. To continue the rotation we need to reverse the direction of current after each half rotation so a split ring is used to flip current...