Two identical conducting spheres are separated by distance l. One carries charge 4×10⁻⁸ C and the other is neutral. They are connected by a conducting wire and then the force between them is 9×10⁻³ N. Find l.
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Question

Two identical conducting spheres are separated by distance l. One carries charge 4×10⁻⁸ C and the other is neutral. They are connected by a conducting wire and then the force between them is 9×10⁻³ N. Find l.

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G1 Physics · Accepted Answer

After connection, equal spheres share charge equally, so each gets q=2×10⁻⁸ C. Using F=kq²/l²: 9×10⁻³=9×10⁹(2×10⁻⁸)²/l². Thus l²=4×10⁻⁴ m² and l=2×10⁻² m=2 cm.