Dual Nature Of Light Question 42
Question: In Millikan oil drop experiment, a charged drop of mass $ 1.8\times {{10}^{-14}}kg $ is stationary between its plates. The distance between its plates is 0.90 cm and potential difference is 2.0 kilo volts. The number of electrons on the drop is [MP PMT 1994, 2003; MP PET 1997]
Options:
A) 500
B) 50
C) 5
D) 0
Show Answer
Answer:
Correct Answer: C
Solution:
$ QE=mg\Rightarrow Q=\frac{mg}{E}\Rightarrow n=\frac{mgd}{Ve} $
$ \Rightarrow n=\frac{1.8\times {{10}^{-14}}\times 10\times 0.9\times {{10}^{-2}}}{2\times 10^{3}\times 1.6\times {{10}^{-19}}}=5 $
BETA
