CBSE Class 10 Answered

Parts of a DC Motor

A D.C. motor consists of a rectangular coil made of insulated copper wire wound on a soft iron core. This coil wound on the soft iron core forms the armature. The coil is mounted on an axle and is placed between the cylindrical concave poles of a magnet.

A commutator is used to reverse the direction of flow of current. Commutator is a copper ring split into two parts C₁ and C₂. The split rings are insulated form each other and mounted on the axle of the motor. The two ends of the coil are soldered to these rings. They rotate along with the coil. Commutator rings are connected to a battery. The wires from the battery are not connected to the rings but to the brushes which are in contact with the rings.

Two small strips of carbon, known as brushes press slightly against the two split rings, and the split rings rotate between the brushes.

When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn towards the right, causing rotation.

When the coil turns through 90⁰, the brushes lose contact with the commutator and the current stops flowing through the coil.

Now when the coil turns through 180⁰, the sides get interchanged. As a result the commutator ring C₁ is now in contact with brush B₂ and commutator ring C₂ is in contact with brush B₁. Therefore, the current continues to flow in the same direction.