Question

A coil has a self inductance of $10 mH$. What is the maximum magnitude of the induced emf in the inductor when a current $I=0.1 \sin 200 t A$ is sent through it?

• A. $0.3\, V$
• B. $0.2\, V$
• C. $0.1\, V$
• D. $0.4\,V$

Answer 1

Answer: (B)

$e = L \frac{ dI }{ dt }$
$\frac{ dI }{ dt }=\frac{ d }{ dt }(0.1 \sin 200 t )$
$\frac{ d I}{ dt }=200 \times 0.1 \cos 200 t$
$\left(\frac{ d I}{ dt }\right)_{\max }=200 \times 0.1$ (for $\max =\cos 200 t =1)$
$e=L \frac{d I}{d t}$
$\Rightarrow 10 \times 10^{-3} \times 200 \times 0.1$
$e =0.2\, V$