PhysicsJEE Main 22 Jan 2026, Shift 1·Q25·Numerical·Moderate

Electromagnetic Induction · Inductance

Inductance of a coil with

10^{4}

turns is 10 mH and it is connected to a dc source of 10 V with internal resistance of

10\ \Omega

. The energy density in the inductor when the current reaches

\left(\dfrac{1}{e}\right)

of its maximum value is

\alpha\pi\times\dfrac{1}{e^2}\ \mathrm{J/m^3}

. The value of

\alpha

is . (

\mu_0 = 4\pi\times10^{-7}

Tm/A). (Take the length of the coil as 1 m)

We corrected a printing error in the original paper

Assumption “Take the length of the coil as 1 m” added; the source gives neither the length nor the turns per unit length, and the key 20 needs $n = 10^4$ turns/m (consistent with $L = 10$ mH for a long solenoid).

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Electromagnetic Induction · Inductance

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