Answer to Question #99793 in Electric Circuits for Sridhar

Question

A circuit when connected to an AC source of 12 V gives a current of 0.2 A. The same circuit when connected to a DC source of 12 V, gives a current of 0.4 A. The circuit is
(1) Series LCR
(2) Series LR
(3) Series RC
(4) Series LC

Answer 1

Since the current increases at DC voltage applied, it means that the total resistance (or impedance) decreases at zero frequency. Hence, it is a series LR circuit:

$$I=\frac{V}{\sqrt{R^2+(\omega L)^2}}.$$