In dc machines, the armature windings are placed on the rotor because of the necessity for

In dc machines, the armature windings are placed on the rotor because of the necessity for 

(1) electromechanical energy conversion (2) generation of voltage (3) commutation (4) development of torque
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2 Answers

Answer :

In dc machines, the armature windings are placed on the rotor because of the necessity for commutation 

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Answer :

3 

Commutation
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