JEE Main 2026 · 4 Apr · Shift 1 · Physics Q40

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PhysicsSingle correct+4 / -1Question 40 of 75

A parallel plate air capacitor is connected to a battery. The plates are pulled apart at uniform speed $v$ . If $x$ is the separation between the plates at any instant, then the time rate of change of electrostatic energy of the capacitor is proportional to $x^\alpha$ , where $\alpha$ is ________.

-2

-1

Answer and worked solution

Official answer: A

Constant V. $U=\dfrac{\varepsilon_0AV^2}{2x}$ .

Rate. $\dfrac{dU}{dt}=-\dfrac{\varepsilon_0AV^2}{2x^2}v\propto x^{-2}$ , so $\alpha=-2$ .

(A)

Topics:Energy stored in a capacitor

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JEE Main 2026 · 4 Apr · Shift 1, Physics question 40