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A uniformly charged disc of radius R having surface charge density σ is placed in the xy plane with its center at the origin. Find the electric field…

JEE Main 2021 — Physics Electromagnetism

2021mcqhard

A uniformly charged disc of radius RRR having surface charge density σ\sigmaσ is placed in the xyxyxy plane with its center at the origin. Find the electric field intensity along the zzz-axis at a distance ZZZ from origin:

Official previous-year question

Held on 27 Aug 2021 · Verified 6 Jul 2026.

Options

  1. A

    E=2ϵ0σ(1(Z2+R2)1/2+Z)E=\frac{2{\epsilon }_{0}}{\sigma }(\frac{1}{{({Z}^{2}+{R}^{2})}^{1/2}}+Z)E=σ2ϵ0​​((Z2+R2)1/21​+Z)

  2. B

    E=σ2ϵ0(1+Z(Z2+R2)1/2)E=\frac{\sigma }{2{\epsilon }_{0}}(1+\frac{Z}{{({Z}^{2}+{R}^{2})}^{1/2}})E=2ϵ0​σ​(1+(Z2+R2)1/2Z​)

  3. C

    E=σ2ϵ0(1−Z(Z2+R2)1/2)E=\frac{\sigma }{2{\epsilon }_{0}}(1-\frac{Z}{{({Z}^{2}+{R}^{2})}^{1/2}})E=2ϵ0​σ​(1−(Z2+R2)1/2Z​)

  4. D

    E=σ2ϵ0(1(Z2+R2)+1Z2)E=\frac{\sigma }{2{\epsilon }_{0}}(\frac{1}{({Z}^{2}+{R}^{2})}+\frac{1}{{Z}^{2}})E=2ϵ0​σ​((Z2+R2)1​+Z21​)

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