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The magnetic field at a point inside a ...

The magnetic field at a point inside a 2.0 mH inductor coil becomes 0.80 of its maximum value in `20 mu s ` when the inductor is joined to a battery. Find the resistance of the circuit.

A

`20 Omega `

B

`40 Omega `

C

`80 Omega `

D

`160 Omega `

Text Solution

Verified by Experts

The correct Answer is:
D
`i=i^(0)(1-e^(-t//tau))`
`0.8 = 1-e^(-t//tau)`
`implies (t)/(tau) = ln 5 implies (20 xx 10^(-6))/(2 xx 10^(-3)) xx R = 1.6 implies R = 160 Omega`
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