Two charged spheres A and B each with charge \(q\), force \(F\). A third uncharged sphere touches A, then B, then is removed. New force between A and B is:

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NEET Physics QUESTION #1038

Question 1

\(\dfrac{F}{2}\)
\(\dfrac{3F}{8}\)(Correct)
\(\dfrac{3F}{5}\)
\(\dfrac{2F}{3}\)

Correct Answer Explanation

After touching A: charge on A \(= q/2\), uncharged sphere \(= q/2\). After touching B (charge \(q\)): total \(= q/2+q = 3q/2\), shared equally so each gets \(3q/4\). Final charges: A \(= q/2\), B \(= 3q/4\). New force: \(F' = k\frac{(q/2)(3q/4)}{r^2} = \frac{3}{8}kq^2/r^2 = \frac{3F}{8}\).

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