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Two electric dipoles aligned parallel to each other and having the same axis exert a force F on each other, when a distance d apart. If the dipoles are a distance 2d apart, then the mutual force between them would be—
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- F/ 2
- F/ 4
- F/ 8
- F/ 16
Correct Option: D
The force of repulsion between the two dipoles
| F = |  | 1 – |  | 2πεd2 | [1 + (I2/d2)] |
Assuming that I << d, we have
| F = | | 1 – 1 + | | 2πεd2 | 2 | d2 |
| F = | 2πεd2 |
Therefore, if with distance d, the force is F, the force with distance 2d would be F/16.
