Doubtclip is an AI tutor that turns any homework or exam doubt into a step-by-step whiteboard video lesson with diagrams, formulas, and voice explanation.

Which subjects and exams does it support?

It supports Physics, Chemistry, Mathematics/Calculus and related STEM doubts for school boards, JEE, NEET, and global high-school / undergrad practice.

How do I get a video solution?

Upload a photo of the question or paste the text, sign in, and Doubtclip generates a whiteboard-style explanation video you can watch and share.

Is Doubtclip available worldwide?

Yes. Doubtclip is a web app for students globally. Lessons are available in English and Hinglish.

Capacitors

JEE Main level, numerical answer, medium

135 of 180

Question 135 of 180

A parallel plate capacitor whose capacitance $C$ is $14pF$ is charged by a battery to a potential difference $V=12V$ 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)

Show answer and solution

Answer: 864

{U}_{i}=\dfrac{1}{2}\times 14\times 12\times 12pJ\left(∵U=\dfrac{1}{2}C{V}^{2}\right)

=1008pJ

{U}_{f}=\dfrac{1008}{7}pJ=144pJ\left(∵{C}_{m}=k{C}_{0}\right)

Mechanical energy

=\Delta U

=1008-144

=864pJ

JEE Main question paper PDF

Open a shift to read the full paper on this page, or download it.

JEE Main 2025 Apr 2 Shift 1 question paper

Open Download PDF

Opening paper…

Explain it as a whiteboard videoStep-by-step, in Hinglish or English. Your first video needs no login.Solved it on paper but got it wrong?Upload a photo of your working. Mistake Doctor marks the exact line that broke.

See it move: Capacitors, dielectrics and RC circuits simulationDrag the sliders and watch the numbers in this question change.

More Physics practice

JEE Main Physics practice question on Capacitors (Force and Energy stored in capacitor), with the answer and a step-by-step solution. Scan a question from your own book or paper to get a whiteboard video.