Two point sized spheres each holding a charge Q are kept at certain se...
- First, let's consider the initial scenario with two point sized spheres each holding a charge Q kept at a certain separation. The repulsive force between them is F.
- **Force between two charged spheres:** The repulsive force between two charged spheres can be calculated using Coulomb's law, which states that the force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. Mathematically, F = k(Q^2/r^2), where k is the Coulomb's constant.
- Now, when a third identical and uncharged sphere is touched with the first sphere and kept exactly mid-way between the first and second spheres, the charges redistribute themselves due to induction.
- **Charge redistribution:** The uncharged sphere becomes polarized when in contact with the charged sphere, resulting in the transfer of some charge to the uncharged sphere. As a result, the uncharged sphere acquires a charge -Q, while the first sphere retains a charge of Q.
- The third sphere is now attracted to the first sphere due to the opposite charges. The force acting on the third sphere can be calculated using Coulomb's law again. Since the distance between the first and third spheres is now half of the original separation, the force acting on the third sphere will be 4F.
- **Force on the third sphere:** The force on the third sphere is 4 times the original repulsive force between the two charged spheres. This is because the charges have redistributed, leading to an attractive force between the first and third spheres.
- In conclusion, the force acting on the third sphere is 4F when it is touched with the first charged sphere and kept exactly mid-way between the two charged spheres.
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