Electro Magnetic Induction And Alternating Currents Question 519
Question: The back e.m.f. induced in a coil, when current changes from 1 ampere to zero in one milli‑second, is 4 volts, the self-inductance of the coil is [MP PET/PMT 1988]
Options:
A) 1 H
B) 4 H
C) $ {{10}^{-3}} $ H
D) $ 4\times {{10}^{-3}} $ H
Show Answer
Answer:
Correct Answer: D
Solution:
$ e=-L\frac{di}{dt} $ but e =4V and
$ \frac{di}{dt}=\frac{0-1}{{{10}^{-3}}}=-1/{{10}^{-3}} $
$ \therefore \ \frac{-1}{{{10}^{-3}}}(-L)=4\Rightarrow L=4\times {{10}^{-3}}henry $
