Twenty seven drops of same size are charged at 220 V each. They combine to form a bigger drop. Calculate the potential of the bigger drop.

1. 660 V

2. 1320 V

3. 1520 V

4. 1980 V

Doubtly Asked 30 Oct 2026 NEET UG 2021 Practice test neet Save WhatsApp Report

1 answer

Best answer

Answer: 4. 1980 V

Key idea: total charge and volume are conserved when drops merge.

Volume: \(\tfrac43\pi R^3=27\cdot\tfrac43\pi r^3\Rightarrow R=3r\).
Charge: \(Q=27q\).
\(V_{big}=\dfrac{kQ}{R}=\dfrac{k\cdot27q}{3r}=9\cdot\dfrac{kq}{r}=9\times220=1980\) V.

Option 4.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

Was this answer helpful?