Discussion
The starting current of a dc motor connected directly to full voltage is large because
Answer: A
Correct answer: there is no back emf at standstill
From \( V = E + I_aR_a \) with \( E = 0 \) at rest, the current is limited only by the armature resistance, which is deliberately small - a fraction of an ohm. A machine that draws 20 A running might draw several hundred at switch-on. The remedy is to insert resistance and remove it as the back emf builds up, or, in a converter drive, to start at a low armature voltage and raise it.
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