Electromagnetic Induction - Result Question 9
9. The current $i$ in a coil varies with time as shown in the figure. The variation of induced emf with time would be
[2011]
(a)
(b)
(c)
(d)
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Answer:
Correct Answer: 9. (a)
Solution:
- (a) $e=-L \frac{di}{dt}$
During 0 to $\frac{T}{4}, \frac{di}{dt}=$ const.
$\therefore e=-ve$
During $\frac{T}{4}$ to $\frac{T}{2}, \frac{di}{dt}=0$
$\therefore e=0$
During $\frac{T}{2}$ to $\frac{3 T}{4}, \frac{di}{dt}=$ const.
$\therefore e=+ve$
Thus graph given in option (a) represents the variation of induced emf with time.
Inductance does not play any role till there is a constant current flowing in the circuit. It opposes any change in the current in the circuit.
