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Two isolated spherical conductors B and C have the same radius and initially carry equal charges. When they are separated by a fixed distance, the repulsive force between them is F. Now an identical uncharged spherical conductor is first touched to B, then to C, and finally taken away. What is the resulting repulsive force between B and C?

1. F/8
2. 3F/4
3. F/4
4. 3F/8

Correct answer: 3F/8

Solution

When the uncharged conductor touches B, it shares charge, reducing B's charge and increasing the charge of the uncharged conductor. After touching C, the charge distribution changes again, resulting in a new charge configuration for both B and C. The final repulsive force is calculated based on the new charges, which results in a force of 3F/8.

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