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Physics · Electrostatics

JEE Main 2025 — 8 April, Evening Shift — Question 61

Two metal spheres of radius RR and 3R3 R have same surface charge density σ\sigma. If they are brought in contact and then separated, the surface charge density on smaller and bigger sphere becomes σ1\sigma_{1} and σ2\sigma_{2}, respectively. The ratio σ1σ2\frac{\sigma_{1}}{\sigma_{2}} is

  1. Option A:

    9

  2. Option B:

    3

    Correct
  3. Option C:

    19\frac{1}{9}

  4. Option D:

    13\frac{1}{3}

Answer: B

Step-by-step solution

v1=v2⇒Q1R1=Q2R2⇒σ1R12R1=σ2R22R2v_{1}=v_{2} \Rightarrow \frac{Q_{1}}{R_{1}}=\frac{Q_{2}}{R_{2}} \Rightarrow \frac{\sigma_{1} R_{1}^{2}}{R_{1}}=\frac{\sigma_{2} R_{2}^{2}}{R_{2}}

⇒σ1σ2=R2R1=3\Rightarrow \frac{\sigma_{1}}{\sigma_{2}}=\frac{R_{2}}{R_{1}}=3

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Paper
8 April, Evening Shift
Subject
Physics
Chapter
Electrostatics
Topic
Properties of Conductors and Redistribution of Charge

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