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Question: Answered & Verified by Expert
An oil drop of the radius 2 mm with a density 3 g cm-3 is held stationary under a constant electric field 3.55×105 V m-1 in the Millikan's oil drop experiment. What is the number of excess electrons that the oil drop will possess? consider g=9.81 m s-2.
PhysicsDual Nature of MatterJEE MainJEE Main 2021 (18 Mar Shift 1)
Options:
  • A 48.8×1011
  • B 1.73×1010
  • C 17.3×1010
  • D 1.73×1012
Solution:
2720 Upvotes Verified Answer
The correct answer is: 1.73×1010
qE=MgneE=ρ43πr3×g
n×1.6×10-19×3.55×105=3×103×43×π×2×10-33×9.81
n=173×10(3-9-5+19)n=1.73×1010.

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