A polythene piece rubbed with wool is found to have negative charge of 3.2 x 10-7 C. Estimate the number of electrons transferred from wool to polythene.

According to quantisation of charge, we have Q=n e, where e=1.6 x 10-19 (the charge of electron). Therefore, the total number of electrons transferred from wool to polythene isn=qe=3.2×10−71.6×10−19=2×1012