A spherical drop of water carries a charge of `10xx10^(-12)C` and has a potential of 100V at its surface.
What is the radius of the drop ?

Explanation

Charge of a spherical water drop,
`Q = 10 xx10^(-12)C`
`= 10xx10^(-12)xx3xx10^(9)` esu of charge
`= 3xx10^(-2)` esu of charge
Potential of the drop, `V= (100)/(300)= (1)/(3)` statV
Capacitance of the drop, `C= (Q)/(V) = (3xx10^(-2))/(1/3)= 0.09` statF
In CGS units, the radius of a spherical conductor = its capacitance.
Radius of the drop, `r = 0.09 cm`.