A series circuit is connected to a battery of emf

PHYSICS · Single correct · AP · Physics C: Electricity and Magnetism · Electromagnetic Induction · Electromagnetic Induction

Problem

A series L−RL-R circuit is connected to a battery of emf VV. If the circuit is switched on at t=0t = 0, then the time at which the energy stored in the inductor reaches (1n)\left(\frac{1}{n}\right) times of its maximum value, is: (1) LRln⁡(nn−1)\frac{L}{R} \ln\left(\frac{\sqrt{n}}{\sqrt{n}-1}\right) (2) LRln⁡(n+1n−1)\frac{L}{R} \ln\left(\frac{\sqrt{n}+1}{\sqrt{n}-1}\right) (3) LRln⁡(nn+1)\frac{L}{R} \ln\left(\frac{\sqrt{n}}{\sqrt{n}+1}\right) (4) LRln⁡(n−1n)\frac{L}{R} \ln\left(\frac{\sqrt{n}-1}{\sqrt{n}}\right)

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