Electrostatics Question 397

Question: An oil drop having charge 2e is kept stationary between two parallel horizontal plates 2.0 cm apart when a potential difference of 12000 volts is applied between them. If the density of oil is900kg/m3 , the radius of the drop will be [AMU 1999]

Options:

A) 2.0×106m

B) 1.7×106m

C) 1.4×106m

D) 1.1×106m

Show Answer

Answer:

Correct Answer: B

Solution:

In equilibrium QE = mg therefore Q.Vd=mg=(43πr3ρ)g

therefore 2×1.6×1019×120002×102=43πr3×900×10

therefore  r=1.7×106m



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