JEE Main 2021PhysicsCapacitanceMediumNumerical

JEE Main 2021 — Capacitance Question with Solution

JEE Main 2021 (17 Mar Shift 1)

Question

A parallel plate capacitor whose capacitance C is 14 pF is charged by a battery to a potential difference V=12 V between its plates. The charging battery is now disconnected and a porcelain plate with k=7 is inserted between the plates, then the plate would oscillate back and forth between the plates with a constant mechanical energy of _______ pJ.

(Assume no friction)

Enter your answer

Show full solutionCorrect answer: 864
Correct answer
864

Step-by-step explanation

Ui=12×14×12×12 pJ  ∵U=12CV2

=1008 pJ

Uf=10087pJ=144 pJ  ∵Cm=kC0

Mechanical energy=ΔU

=1008-144

=864 pJ

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About this question

This is a previous-year question from JEE Main 2021, covering the Capacitance chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.