Q. 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
A) $2.7 \times 10^{5}$
B) $2.6 \times 10^{5}$
C) $2.5 \times 10^{5}$
D) $2.4 \times 10^{5}$
Explanation
(c) $E = \ \frac{1}{4\pi\varepsilon_{0}}.\frac{ne}{r^{2}} \Rightarrow n = \frac{Er^{2}}{e}.4\pi\varepsilon_{0}$
$\Rightarrow n = \frac{0.036 \times 0.1 \times 0.1}{9 \times 10^{9} \times 1.6 \times 10^{- 19}} = \frac{360}{144} \times 10^{5} = 2.5 \times 10^{5}N/C$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.