Question

The current passing through an inductor coil of 5H is decreasing at the rate of 2A/s, the emf developed across the coil is

• A. $+10.0V$
• B. $-10.0V$
• C. $+2.5V$
• D. $-2.5V$

Answer 1

Answer: (A)

$+10.0V$

Answer 2

If on changing current through the coil, the emf induced in the coil ise, then by Faradays 2nd law, we have $e=-L\frac{\Delta i}{\Delta t}$ where, $\frac{\Delta i}{\Delta t}$ is rate of change of current. Given, $L=5H,\text{ }\frac{\Delta i}{\Delta t}=-2A/s$ (decreasing) $\therefore$ $e=-5\times (-2)=+10V$