JEE PYQ: Electrostatics Question 8
Question 8 - 2021 (25 Feb Shift 1)
512 identical drops of mercury are charged to a potential of 2 V each. The drops are joined to form a single drop. The potential of this drop is ______ V.
Show Answer
Answer: 128
Solution
Let charge on each drop $= q$, radius $= r$. $V = \frac{kq}{r} = 2$. For the big drop: $\frac{4}{3}\pi R^3 = 512 \times \frac{4}{3}\pi r^3$, so $R = 8r$. Total charge $= 512q$. $V’ = \frac{k(512q)}{R} = \frac{512}{8} \times \frac{kq}{r} = 64 \times 2 = 128$ V.
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