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A coil of inductance 8.4 mH and resistan...

A coil of inductance `8.4 mH` and resistance `6` `Omega` is connected to a `12 V` battery. The current in the coil is `1.0 A` at approximately the time.

A

500 ms

B

20 ms

C

35 ms

D

1 ms

Text Solution

Verified by Experts

The correct Answer is:
4
Current developed with time in a coil of inductance
`I=(V)/(R)(1-e^-t/e) `where `tau=L/R` we have` tau=(8.4mH)/(6Omega)` =1.4 ms
Hience`1A=((12V))/(6Omega)(1-e^(-t/1.4ms)`or`e^(-t/14ms)=1-(1)/(2)=(1)/(2)`
or`-t//1.4mms=In((1)/(2))=-0.693`
or`t=1.4xx0.693`ms = 0.97 ms approx1 ms`
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