Question 915: Electrostats & Capacitance

Question

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

Accepted Answer

Let charge and radius of smaller drop is q and r
respectively
For smaller drop, V = $${{kq} \over r} = 220\,V$$
Let R be radius of bigger drop,
As volume remains the same
$$\left( {{4 \over 3}\pi {r^3}} ight) 	imes 27 = {4 \over 3}\pi {R^3}$$
$$ \Rightarrow $$ R = 3r
Now, using charge conservation,
Q = 27q
V
big drop
= $${{kQ} \over r} = {{k\left( {27q} ight)} \over r} = 9\left( {{{kq} \over r}} ight)$$
= 9 $$ 	imes $$ 220 = 1980 V

Answer

1980 V

Answer

660 V

Answer

1320 V

Answer

1520 V

Electrostats & Capacitance

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

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