Physics · Capacitors and R-C Circuits

JEE Main 2025 — 4 April, Evening Shift — Question 57

Three parallel plate capacitors $C_{1}, C_{2}$ and $C_{3}$ each of capacitance $5 \mu \mathrm{~F}$ are connected as shown in figure. The effective capacitance between points $A$ and $B$ , when the space between the parallel plates of $C_{1}$ capacitor is filled with a dielectric medium having dielectric constant of 4 , is:

Option A:
$30 \mu \mathrm{~F}$
Option B:
$9 \mu \mathrm{~F}$
Correct
Option C:
$22.5 \mu \mathrm{~F}$
Option D:
$7.5 \mu \mathrm{~F}$

Answer: B

Step-by-step solution

$C_{e q}=\left(\frac{K C \cdot C}{K C+C}\right)+C$

$=\left(\frac{K}{K+1}\right) C+C$

$=\frac{4}{5} \times 5+5=9 \mu \mathrm{~F}$

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 4 April, Evening Shift
Subject: Physics
Chapter: Capacitors and R-C Circuits
Topic: Combination of Capacitors and Circuit Analysis