Calculate the ratio of electric to gravitational force between two electrons.

Explanation

The electric force `= e^2/(4 pi epsilon_0r^2)`
and the gravitatioN/Al force `= (G(m_e)^2)/r^2`
The ratio is `e^2/(4 pi epsilon_0 G(m_e)^2)`
`= (9xx10^9 (N-m^2)/C^2xx(1.6xx10^-19C)^2)/(6.67xx10^-11 (N-m^2)/kg^2xx(9.1xx10^-31 kg)^2)= 4.17xx10^42`.