Question

The ratio of electric force between two electrons to the gravitational force between them is of the order

• A. 10${}^{42}$
• B. 10${}^{39}$
• C. 10${}^{36}$
• D. 1

Answer 1

The correct option is A 10${}^{42}$

The electric force between two electrons is $F_e=\frac{k{e}^2}{r^2}$

and gravitational force between two electrons is $F_g=\frac{G{m}_e^2}{r^2}$

Thus, $\frac{F_e}{F_g}=\frac{k{e}^2}{G{m}_e^2}=\frac{(9\times {10}^9)(1.6\times {10}^{-19}{)}^2}{(6.67\times {10}^{-11})(9.1\times {10}^{-31}{)}^2}=4.17\times {10}^{42}\sim {10}^{42}$