JEE MAIN - Physics (2022 - 25th June Evening Shift - No. 25)

27 identical drops are charged at 22V each. They combine to form a bigger drop. The potential of the bigger drop will be _____________ V.

Answer

198

Let the charge on one drop is q and its radius is r.

So for one drop $$V = {{kq} \over r}$$

For 27 drops merged new charge will be Q = 27 q and new radius is R = 3r

So new potential is

$$V' = {{kQ} \over R} = 9{{kq} \over r} = 9 \times 22$$ V

= 198 V