COMEDK · Physics · 17. Electrostatics

The force between two electric point charges at rest in air is \(F_1\) When the same arrangement is kept inside water, the force between them is \(F_2\). Which of the following statement is correct?

A \(F_2>F_1\)
B \(F_2=0\)
C \(F_2=F_1\)
D \(F_2< F_1\)

Verified Solution

Answer & Solution

Correct Answer

(D) \(F_2< F_1\)

Step-by-step Solution

Detailed explanation

The electrostatic force between two point charges \(q_1\) and \(q_2\) separated by a distance \(r\) in a medium with dielectric constant \(K\) is given by Coulomb's law as \(F = \dfrac{1}{4 \pi \epsilon_0 K} \dfrac{q_1 q_2}{r^2}\). In air, the dielectric constant…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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