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JEE Main 2021 (20 Jul, Shift 1) · Electric Charge & Coulomb's Law

Electric Charge & Coulomb's Law question from JEE Main 2021 (20 Jul, Shift 1)

Q53JEE Main 2021 · 20 JUL · SHIFT 1Easy

Electric Charge & Coulomb's Law

A certain charge Q is divided into two parts q and (Q $-$ q). How should the charges Q and q be divided so that q and (Q $-$ q) placed at a certain distance apart experience maximum electrostatic repulsion?

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Answer: (a)

$F \propto q(Q-q)$ ; $\dfrac{dF}{dq} = Q-2q = 0$ .
$q = \dfrac{Q}{2} \Rightarrow Q = 2q$
So the answer is (a) $Q = 2q$ .

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