In Millikan's oil drop experiment an oil drop of radius `r` and change `Q` is held in equilibrium between the plates of a charged parallel plate capacitor when the potential change is `V`. To keep a drop radius `2r` and with a change `2Q` is equilibriu between the plates the potential difference `V'` required is:

Options

A. `V`
B. `2V`
C. `4V`
D. `8V`

Answer

C

Explanation

`:'qE=mg`
`q(V/d)=(4/3pir^3rho)g`
Vpropr^3/q`