Electrostatics Question 351
Question: The number of electrons to be put on a spherical conductor of radius$ 0.1m $ to produce an electric field of $ 0.036N/C $ just above its surface is [MNR 1994; KCET (Engg.) 1999; MH CET (Med.) 2001]
Options:
A) $ 2.7\times 10^{5} $
B) $ 2.6\times 10^{5} $
C) $ 2.5\times 10^{5} $
D) $ 2.4\times 10^{5} $
Show Answer
Answer:
Correct Answer: C
Solution:
$ E=\frac{1}{4\pi {\varepsilon _{0}}}.\frac{ne}{r^{2}} $
therefore $ n=\frac{Er^{2}}{e}.4\pi {\varepsilon _{0}} $
therefore $ n=\frac{0.036\times 0.1\times 0.1}{9\times 10^{9}\times 1.6\times {{10}^{-19}}}=\frac{360}{144}\times 10^{5} $ = 2.5x 105 N/C.
