Question

explain the DC motor under following sub-topic? a) construction, b) working principle, c) Diagram, d) Uses answer
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Answer 1

Answer:

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Explanation:

It is a machine which converts electrical energy to mechanical energy. It is based on the principle of magnetic effect of current.

Construction: It essentially consists of the following parts:

(a) Field magnet (NS): In common dynamo it is a horse shoe magnet but for strong field electromagnet is used.

(b) Armature (ABCD): It consists of a coil of insulated copper wire, wound on soft iron core. It is rotated between the pole pieces by some external device.

(c) Split ring commutator (S1,S2): The commutator is just a copper ring split into two halves S1 and S2 insulated from each other and the shaft. The ends of the coil are connected to S1 and S2, respectively.

(d) Brushes (B1,B2): These are carbon strips which slide against the split rings S1 and S2. The current induced in the armature flows through these brushes in the enternal circuit.

Working: The armature ABCD is rotated in the clock wise direction in the field and at any instant, S1 is in contact with B1 and S2with B2. Under such situation AB will come up the plane of paper and CD will go down. They by fleming right hand rule, the direction of induced current will be along ABCD S1B1RB2S2A. So, the current in the external circuit flows from B1 to B2 through R.

After half rotation, split ring S2 is in contact with B1 and S1 and the arms. AB and CD interchange their is positions. Now again when the coil is rotated clockwise CD comes up the plane of paper and AB goes down. Then by fleming right hand rule the direction of induced current is DCBA S2B1RB2S1D. Hence, in the external circuit the current flows from B1 to B2 through R. So, the current in the enternal circuit flows in the same direction. Hence, direct current is obtained.