Discussion
The field of a dc motor should be connected before the armature at starting so that
Answer: B
Correct answer: the flux is at its full value when armature current flows
Torque is \( k\Phi I_a \), so the machine needs full flux at the moment the armature is energised, or it will produce little torque for a very large current and may fail to accelerate. There is a second reason: with a weak field the machine would run away as it accelerated. The field circuit is highly inductive and takes time to establish its current, which is why the field switch closes first.
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