**Example:**If $F_{g}$ and $F_{e}$ are gravitational and electrostatic forces between two electrons at a distance $0.1$ $m$ then $F_{g}/F_{e}$

is in what order?

**Solution:**Gravitational force $F_{g}=r_{2}Gm_{2} $

Electrostatic force $F_{e}=r_{2}Kq_{2} $

$F_{e}F_{g} =Kq_{2}Gm_{2} $

where $G=$Universal gravitational constant and $K=1/4πϵ_{0}$

$G=6.67×10_{−11}$ and $K=9×10_{9}$

Mass of an electron is $9.31×10_{−31}$ and Charge of an electron is $1.6×10_{−19}$

Hence, $F_{g}/F_{e}=Gm_{2}/Kq_{2}$ is of the order of $10_{−11−62−9+38}=10_{−43}$