JEE Main 2015PhysicsCapacitanceHardMCQ

JEE Main 2015 — Capacitance Question with Solution

JEE Main 2015 (10 Apr Online)

Question

In the given circuits a and b, switches S1 and S2 are closed at t=0 and kept close for a long time. The variation of currents in the two circuits for t≥0 are shown in the options. (Figures are schematic and not drawn to scale.)

Choose an option

Show full solutionCorrect option: B
Correct answer
B

Step-by-step explanation

In C-R series circuit,
q=q0 1-e-tτ
⟹q=CE 1-e-tRC
∴ I=dqdt
=CERC+e-tRC
I=ER e-tRC
⟹ the urrent decays exponentially. In L-R series circuit,
I=I0(1-e-tτ)
⇒I0=ER  
⇒I=ER 1-e-RtL   
⟹ current grows exponentially.

∴ For C-R circuit,



For L-R circuit,

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About this question

This is a previous-year question from JEE Main 2015, 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.