Consider a coin of Question 20. It is electrically neutral and contains equal amounts of positive and negative charge of magnitude 34.8 kC. Suppose that these equal charges were concentrated in two point charges separated by:
(i) 1 cm `(-1/2) xx` displacement of the one paisa coin)
(ii) 100 m (-length of a long building)
(iii) `10^(6)` m (radius of the earth).
Find the force on each such point charge in each of the three cases. What do you conclude from these results ?

Explanation

Here, `r_(1) = 1 cm = 10^(-2)` m
`r_(2) = 100 m`
`r_(3) = 10^(6) m`
`1/(4pi epsilon_(0)) = k = 9 xx 10^(9)`
(i) `F_(1) = (k|q|^(2))/(r_(1)^(2)) =(9 xx 10^(9) xx (3.48 xx 10^(4))^(2))/(10^(-2))^(2)`
`=1.09 xx 10^(23)` N
(ii) `F_(2) = (k|q|^(2))/r_(2)^(2) = (9 xx 10^(9) xx (3.48 xx 10^(4))^(2))/(100)^(2) = 1.09 xx 10^(15)` N
(iii) `F_(3) = (k|q|^(2))/r_(3)^(2) = (9 xx 10^(9) xx (3.48 xx 10^(4))^(2))/(10^(6))^(2)`
`=1.09 xx 10^(7)` N
Conclusion : Here, the force between charges is much more hence, it is difficult to disturb electrical neutrality of matter.