COMEDK · Physics · 17. Electrostatics
Two charged spheres of \(-20 \mu \mathrm{C}\) and \(60 \mu \mathrm{C}\) are kept at a certain distance. They are touched and kept again at the same distance. What is the ratio of force experienced before and after?
- A \(1: 3\)
- B 3 : 1
- C 2 : 1
- D \(1: 2\)
Answer & Solution
Correct Answer
(B) 3 : 1
Step-by-step Solution
Detailed explanation
Let the charges on the two spheres be \(q_1 = -20 \mu C\) and \(q_2 = 60 \mu C\). Let the distance between them be \(r\). The electrostatic force before touching is given by Coulomb's law: \(F_1 = k \dfrac{|q_1 q_2|}{r^2} = k \dfrac{|(-20)(60)|}{r^2} = k \dfrac{1200}{r^2}\) When…
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