NTA Abhyas 2020
- Exam
- NTA Abhyas
- Year
- 2020
- Subject
- Physics
- Chapter
- Electromagnetic Waves
NTA Abhyas 2020 · Physics · Electromagnetic Waves
An oil drop carrying a charge q has a mass m kg. It is falling...
An oil drop carrying a charge has a mass kg. It is falling freely in air with terminal speed . The electric field required to make the drop move upwards with the same speed is
Options
- A
- B
- C
- D
Correct answer
B.
Step-by-step solution
\dfrac{\text{QV}}{ℓ} = \dfrac{4}{3} \pi r^{3} ρ \text{g}
When the oil drop is falling freely under the effect of gravity is a viscous medium with terminal speed then
mg = 6\piηrv ...(i)
To move the oil drop upward with terminal velocity if is the electric field intensity applied, the
Eq = mg + 6\piηrv = mg + mg = 2mg
When the oil drop is falling freely under the effect of gravity is a viscous medium with terminal speed then
mg = 6\piηrv ...(i)
To move the oil drop upward with terminal velocity if is the electric field intensity applied, the
Eq = mg + 6\piηrv = mg + mg = 2mg