COMEDK · Physics · 17. Electrostatics

Four charges each with charge \(+q\) are placed at the four corners of a square of side \(l\), a charge \(\frac{-q}{4}\) is at centre of the square. Force on the charge at the centre due to other charges is

A \(\frac{K q^2}{l^2}\)
B \(K \frac{\sqrt{2} q^2}{l^2}\)
C zero
D \(K \frac{2 \sqrt{2} q^2}{l^2}\)

Verified Solution

Answer & Solution

Correct Answer

(C) zero

Step-by-step Solution

Detailed explanation

Force due to each \(q\) charge on \(-q / 4\) is balanced by diagonally opposite charge. \(F_{\text {net }}=0\)

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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