Compound alternating current circuits

Explanation of question 7

A coil takes a current of 5A when connected to a 15V DC supply. When connected to a 15V AC supply, the current is 3A. This difference in current is because, when connected to the DC supply, the

  1. coil reactance is zero
  2. coil resistance is zero
  3. coil reactance is infinitely high
  4. coil resistance is infinitely high

The answer is :- 1 Reactance is a frequency dependant quantity. An inductor's reactance is zero at DC, thus it exhibits much less opposition to current flow in a DC circuit than an AC circuit

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