Electrostatics Question 160
Question: $ F _{g} $ and $ F _{e} $ represents gravitational and electrostatic force respectively between electrons situated at a distance 10 cm. The ratio of $ F _{g}/F _{e} $ is of the order of [NCERT 1978; CPMT 1978]
Options:
A) $ 10^{42} $
B) 10
C) 1
D) $ {{10}^{-43}} $
Show Answer
Answer:
Correct Answer: D
Solution:
Gravitational force between electrons $ F _{G}=\frac{G{{(m _{e})}^{2}}}{r^{2}} $
Electrostatics force between electrons $ F _{e}=k.\frac{e^{2}}{r^{2}} $
$ \frac{F _{G}}{F _{e}}=\frac{G{{(m _{e})}^{2}}}{k.e^{2}}=\frac{6.67\times {{10}^{-11}}\times {{(9.1\times {{10}^{-31}})}^{2}}}{9\times 10^{9}\times {{(1.6\times {{10}^{-19}})}^{2}}} $
$ =2.39\times {{10}^{-43}} $
