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The time constant of an inductance coil ...

The time constant of an inductance coil is `2.0xx10^(-3)s`. When a `90Omega` resistance is joined in series, then the time constant becomes `0.5xx10^(-3)s`. The inductance and resistance of the coil are

A

`30 mH`, `30 Omega`

B

`60 mH`, `30 Omega`

C

`30 mH`, `60 Omega`

D

`60 mH`, `60 Omega`

Text Solution

Verified by Experts

The correct Answer is:
B
`(L)/(R ) = 2 xx 10^(-3)` (i)
`(L)/(R + 90) = 0.5 xx 10^(-5)`
From (i) and (ii), on solving, we get
`L = 60 mH` and `R = 30 Omega`
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