Verified Solution • 2025–26 Session moderate

QJEEM21Ph86ec: JEE Main 2021 Physics - Class 12 JEEM21Ph86ec Solution: Two identical conducting spheres with negligible volume have…

Two identical conducting spheres with negligible volume have 2.1 nC and −- 0.1 nC charges, respectively. They are brought into contact and then separated by a distance of 0.5 m. The electrostatic force acting between the spheres is __________ ×\times 10 −- 9 N.

[Given : 4πε0=19×1094\pi {\varepsilon _0} = {1 \over {9 \times {{10}^9}}} SI unit]

Step-by-Step Verified Solution

JEE Main 2021 (Online) 25th February Evening Shift Physics - Electrostatics Question 138 English Explanation 1
When they brought into contact & then separated by a distance = 0.5 m

Then charge distribution will be

JEE Main 2021 (Online) 25th February Evening Shift Physics - Electrostatics Question 138 English Explanation 2

The electrostatic force acting b/w the sphere is

Fe=kq1q2r2{F_e} = {{k{q_1}{q_2}} \over {{r^2}}}

=9×109×1×10−9×1×10−9(0.5)2= {{9 \times {{10}^9} \times 1 \times {{10}^{ - 9}} \times 1 \times {{10}^{ - 9}}} \over {{{(0.5)}^2}}}

=90025×10−9= {{900} \over {25}} \times {10^{ - 9}}

⇒\Rightarrow Fe=36×10−9N{F_e} = 36 \times {10^{ - 9}}N

Related Learning Resources & Exam Preparation

JEE Main PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring