JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumApplication

JEE Main 26 August 2021, Shift 2, Physics Q20

Question 20 of 90 in this shift, Physics question 20 of 30, Section A.

The two thin coaxial rings, each of radius ‘a’ and having charges

+Q

and

-Q

respectively are separated by a distance of ‘s’. The potential difference between the centres of the two rings is :

(1) $\frac{Q}{4\pi\varepsilon_0}\left[\frac{1}{a}-\frac{1}{\sqrt{s^2+a^2}}\right]$
(2) $\frac{Q}{4\pi\varepsilon_0}\left[\frac{1}{a}+\frac{1}{\sqrt{s^2+a^2}}\right]$
(3) $\frac{Q}{2\pi\varepsilon_0}\left[\frac{1}{a}+\frac{1}{\sqrt{s^2+a^2}}\right]$
(4) $\frac{Q}{2\pi\varepsilon_0}\left[\frac{1}{a}-\frac{1}{\sqrt{s^2+a^2}}\right]$ Official answer

Official answer

Option 4

NTA final key.

Chapter: Electrostatic Potential and Capacitance
Topic: Electric Potential
Idea tested: Axial Potential of Ring

Same topic in other shifts

All Electric Potential questions

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.