JEE Main 2022 · 29 Jul · Shift 1 · Physics Q44

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PhysicsSingle correct+4 / -1Question 44 of 90

A coil of inductance 1 H and resistance 100 Ω is connected to a battery of 6 V. Determine approximately :

(a) The time elapsed before the current acquires half of its steady - state value.

(b) The energy stored in the magnetic field associated with the coil at an instant 15 ms after the circuit is switched on. (Given ln2 = 0.693, $e^{-3/2}$ = 0.25)

t = 10 ms; U = 2 mJ

t = 10 ms; U = 1 mJ

t = 7 ms; U = 1 mJ

t = 7 ms; U = 2 mJ

Answer and worked solution

Official answer: C

Half value. $\tau=\frac LR=10$ ms, $t=\tau\ln2\approx7$ ms.

At 15 ms. $I=0.06(1-e^{-1.5})=0.045$ A, $U=\frac12LI^2\approx1.0$ mJ.

(C)

Topics:LR circuits Energy in an inductor

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JEE Main 2022 · 29 Jul · Shift 1, Physics question 44