JEE Main 2026 — Physics Electromagnetism

2026mcqmedium

An inductor of inductance $10$ mH having resistance of $100\,\Omega$ is connected to battery of E.M.F. $1.0$ V through a switch as shown in the figure below. After switch is closed, the ratio of instantaneous voltages across the inductor when the current passing through it is $2$ mA and $4$ mA is _______.

JEE Main 2026 Physics, Electromagnetic Induction — question figure

Official previous-year question

Held on 6 Apr 2026 · Verified 6 Jul 2026.

Options

A
$4/3$
B
$3/4$
C
$5/3$
D
$3/5$

Did you get this right?

Solution

In an LR circuit, the equation for the voltage is given by Kirchhoff's loop law:

$E = L \dfrac{di}{dt} + iR$

The instantaneous voltage across the ideal inductor is the induced EMF, which is given by:

$V_L = L \dfrac{di}{dt} = E - iR$

Given values are:

$E = 1.0$ V

$R = 100\,\Omega$

For current $i_1 = 2$ mA $= 2 \times 10^{-3}$ A, the voltage across the inductor is:

$V_{L1} = 1.0 - (2 \times 10^{-3} \times 100) = 1.0 - 0.2 = 0.8$ V

For current $i_2 = 4$ mA $= 4 \times 10^{-3}$ A, the voltage across the inductor is:

$V_{L2} = 1.0 - (4 \times 10^{-3} \times 100) = 1.0 - 0.4 = 0.6$ V

The ratio of the instantaneous voltages is:

$\dfrac{V_{L1}}{V_{L2}} = \dfrac{0.8}{0.6} = \dfrac{4}{3}$

Answer: $4/3$

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Solution

In an LR circuit, the equation for the voltage is given by Kirchhoff's loop law:

$E = L \dfrac{di}{dt} + iR$

The instantaneous voltage across the ideal inductor is the induced EMF, which is given by:

$V_L = L \dfrac{di}{dt} = E - iR$

Given values are:

$E = 1.0$ V

$R = 100\,\Omega$

For current $i_1 = 2$ mA $= 2 \times 10^{-3}$ A, the voltage across the inductor is:

$V_{L1} = 1.0 - (2 \times 10^{-3} \times 100) = 1.0 - 0.2 = 0.8$ V

For current $i_2 = 4$ mA $= 4 \times 10^{-3}$ A, the voltage across the inductor is:

$V_{L2} = 1.0 - (4 \times 10^{-3} \times 100) = 1.0 - 0.4 = 0.6$ V

The ratio of the instantaneous voltages is:

$\dfrac{V_{L1}}{V_{L2}} = \dfrac{0.8}{0.6} = \dfrac{4}{3}$

Answer: $4/3$

JEE Main 2026 — Physics Electromagnetism

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Solution

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JEE Main 2026 — Physics Electromagnetism

Options

Did you get this right?

Solution

Your note

JEE Main Electromagnetism in other years

More JEE Main Electromagnetism questions

Other Physics topics for JEE Main

Mechanics

Modern Physics

Optics

Thermodynamics

Waves & Oscillations

Keep practicing Electromagnetism