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 $



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