Electromagnetic Induction - Result Question 29
29. A varying current in a coil changes from 10A to zero in $0.5 sec$. If the average e.m.f induced in the coil is $220 V$, the self-inductance of the coil is
(a) $5 H$
(b) $6 H$
(c) $11 H$
(d) $12 H$
[1995]
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Answer:
Correct Answer: 29. (c)
Solution:
- (c) Initial current $(I_1)=10 A$; Final current $(I_2)$ $=0$; Time $(t)=0.5 sec$ and induced e.m.f. $(\varepsilon)=$ $220 V$.
Induced e.m.f. ( $(\varepsilon)$
$=-L \frac{d I}{d t}=-L \frac{(I_2-I_1)}{t}=-L \frac{(0-10)}{0.5}=20 L$
or, $L=\frac{220}{20}=11 H$
[where $L=$ Self inductance of coil]
