Question

A 400 mH coil is connected to an AC source, an RMS current of 6 mA is flowing. Find out the voltage across the coil if the frequency is 1000 Hz.

Answer 1

 The voltage at 1000 Hz:

$$V=IZ,$$

where

$$Z=X_L=2\pi fL.$$

Therefore:

$$V=I\cdot2\pi fL=15\text{ V}.$$