1.

The time constant of an inductance coil is `2 xx 10^(-3) s`. When a `90-Omega` resistance is joined in series, the same constant becomes `0.5 xx 10^(-3) s`. The inductance and resistance of the coil areA. `30 mH`, `30 Omega`B. `60 mH`, `30 Omega`C. `30 mH`, `60 Omega`D. `60 mH`, `60 Omega`

Answer» Correct Answer - 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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