Verified Solution • 2025–26 Session moderate

QJEEM21Ph75de: JEE Main 2021 Physics - Class 11 JEEM21Ph75de Solution: In Millikan's oil drop experiment, what is viscous force acting …

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

Multiple Choice Options

  • A 3.8 ×\times 10 −- 11 N
  • B 3.9 ×\times 10 −- 10 N
  • C 1.8 ×\times 10 −- 10 N
  • D 5.8 ×\times 10 −- 10 N

Step-by-Step Verified Solution

Viscous force = Weight

=ρ×(43πr3)g= \rho \times \left( {{4 \over 3}\pi {r^3}} \right)g

= 3.9 ×\times 10 −- 10

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