Question

A charged oil drop is to be held stationary between two plates separated by the distance of 25 mm. If the mass of the top is 5 ×10^-15 and the charge on it is 10^-18 C, the potential to be applied between the two plates is where is equals to 10 metre per second square.

Answer 1

A charged oil drop is to be held stationary between two plates separated by the distance of 25 mm. If the mass of the top is 5 ×10^-15 and the charge on it is 10^-18 C.

charge on oil drop, q = 10^-18 C

mass of charged oil drop, m = 5 × 10^-15g = 5 × 10^-18Kg

distance between the plates, d = 25mm = 25 × 10^-3 m

at equilibrium,

electrostatic force is balanced by weight of oil drop

or, qE = mg

or, E = mg/q = (5 × 10^-18 × 10)/(10^-18)

= 50 N/C

now, potential = Ed

= 50 × 25 × 10^-3

= 1250/1000 = 1.25 volts

hence, answer is 1.25 volts.