Question

In Millikan's oil drop experiment, what is viscous force acting on an uncharged drop of radius 2.0 × 10^–5 m and density 1.2 × 10³ kgm^–3 ? Take viscosity of liquid = 1.8 × 10^–5 Nsm^–2. (Neglect buoyancy due to air).

(1) 3.8 × 10^–11 N

(2) 3.9 × 10^–10 N

(3) 1.8 × 10^–10 N

(4) 5.8 × 10^–10 N

Answer 1

Correct answer is (2).

Viscous force = Weight