Question

A polythene piece rubbed with wool is found to have a negative charge of $3\times {10}^{-7}$C.

(a) Estimate the number of electrons transferred (from which to which?)

(b) Is there a transfer of mass from wool to polythene?

Answer 1

(a) Since negative charge is on polythene, electrons are transferred from wool to polythene. The no. of electrons transferred are $n=\frac{Totalcharge}{e}=\frac{3\times {10}^{-7}}{1.6\times {10}^{-19}}=1.87\times {10}^{12}\approx 2\times {10}^{12}$

(b) The mass transferred is $m=n\times m_e=2\times {10}^{12}\times 9.31\times {10}^{-31}\approx 1.8\times {10}^{-18}kg$