Question

The current $I$ in an inductance coil varies with time according to the graph given in the figure.

Which one of the following graphs gives the variation of voltage with time across the inductor?

• A.
• B.
• C.
• D.

Answer 1

Answer: (C)

The voltage across an inductor is
$V=-L\frac{di}{dt}$
So the voltage across the inductor will always be opposite to the rate of change of current.
When $\frac{di}{dt}>0$ then $V<0$ and vice versa
Also, the magnitude of $V$ is proportional to the magnitude of $\frac{di}{dt}$ .
When $\frac{di}{dt}$ decreases, $V$ also decreases.