A polythene piece rubbed will wool is found to have a negative charge of `3.0xx10^(-7)C`.
(a) Estimate the number of electrons transferred (from which to which )?
(b) Is there a transfer of mass from wool to polythene?

Explanation

(a) Polythene acquires negative charge when it is rubbed with wool, which means that electrons are transferred from wool to polythene. Let n be the number of electrons transferred from the wool to the polythene piece, then for the given amount of charge we can write:
`q= "ne" rArr n =q/e =(3xx10^(-7))/(1.6xx10^(-19))=1.875xx10^12`
(b)There is a slight gain of mass by the polythene piece as electrons are added to it. So, the mass gained by the polythene piece is:
`Delta_m=nm_e =1.875xx10^12xx9.1xx10^(-31)`
`=1.7xx10^(-18)` kg