Metal sphere A has a charge of - Q. An identical metal sphere B has a charge of 2Q. The magnitude of the electric force on B due to A is F. The magnitude of the electric force on A due to B must be (A) 2F (B) F/4 (C) F/2 (D) F (E) 4F

option D) is correct.

Explanation:

When two charges Q₁ and Q₂ which are unequal in magnitude as well as in nature are at a distance of R then a force F is created between them which is given by the expression

F = k (Q₁ X Q₂) / R²

This force acts equally on both the charges Q₁ and Q₂ irrespective of the fact that they are unequal charges. In other words both Q₁ and Q₂ experience same force F whose value is given above.

In the given case too charges are unequal in magnitude and in nature. They will attract each other with equal force. So if A experiences force F, B too will experience the same force,

Hence option D) is correct.