Question

Suppose you have two small "point" objects separated by a distance of 1 cm. Each object has a diameter of 10 −3 cm. One object has an excess of 3 × 10 10 electrons and the other has an excess of 2 × 10 10electrons on it. What is the electrostatic force that they exert on each other?

Answer 1

Gives

Separation distance (r)=1cm

each object diameter $d=10^{-3}cm<<1cm$

Object assume point partical

Charge $q_1=n_1e\\q_2=n_2e$

$n_1=3\times10^{10} electron$

$n_2=2\times10^{10}electron$

$$q_1=3\times10^{10}\times1.6\times10^{-19}=4.8\times10^{-9}C$$

$$q_1=2\times10^{10}\times1.6\times10^{-19}=3.2\times10^{-9}C$$

Now electrostatic force

$F=\frac{kq_1q_2}{r^2}$

Put value

$F=\frac{9\times10^{9}\times4.8\times10^{-9}\times3.2\times10^{-9}}{0.01^2}$

$F=1.3824\times10^{-3}N$