Two insulated charged copper spheres A and B have their centress separated by a distance of 50 cm . What is the mutual force of electrostatic repulsion if the charges on each is `6.5 xx10^(-7) C ` ? The radii of A and B are neglible compared to the distance of separation
(b) What is the force of repulsion if each sphere is charged bouble the above amount, and the distance between them is halved?

Explanation

Here `q=3xx10^(-7) C ` (negative )and e`=1.6 xx 10^(-19) C `
`therefore `Number of electrons transferred `n =(q)/(e) =(3xx10^(-7))/(1.6xx 10^(-19)) = 1.875xx10 ^(12) =2xx10^(12) `
As polythene piece when rubbed with wool acquires a negative charges, hence electrons have been transferred from wool to polythene.
(b) Yes, there is a transfer of mass from wool to polythene because electrons have mass. The mass transferred `Delta m=n,(m_e) `
` =1.875 xx10 ^(12) xx9.1 xx10^(-31) kg =1.7xx 10 ^(-18) kg infty 2xx10 ^(-18) kg `.
However , this mass transferred is negligible and cannot be detected experimentally.