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

Question

A polythene piece rubbed with wool is found to have a negative charge of $3 	imes 10^{-7}$ C. The transfer of mass from wool to polythene is:

Accepted Answer

When polythene is rubbed with wool, it gains electrons and becomes negatively charged. To find the mass transferred, first calculate the number of electrons ($n$) transferred using quantization of charge $q = ne$. 
$n = \frac{q}{e} = \frac{3 	imes 10^{-7} 	ext{ C}}{1.6 	imes 10^{-19} 	ext{ C}} = 1.875 	imes 10^{12}$.
The mass transferred is the mass of these electrons ($M = n 	imes m_e$). 
$M = 1.875 	imes 10^{12} 	imes 9.1 	imes 10^{-31} 	ext{ kg} \approx 1.7 	imes 10^{-18} 	ext{ kg}$. 
(See NCERT Physics Class 12, Exercise 1.11).

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