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NCERT Class XII Chapter
Electric Charges and Fields
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Question : 11 of 34
Marks: +1, -0
A Polythene piece rubbed with wool is found to have a negative charge of 3 × 10−710^{-7} C.
(a) Estimate the number of electrons transferred (from which to which?)
(b) Is there a transfer of mass from wool to polythene?
Solution:  
(a) q = ne or n = qe\frac{q}{e} = 3×10−71.6×10−19\frac{3\times10^{-7}}{1.6\times10^{-19}} = 1.875 × 101210^{12}
so, 1.875 × 101210^{12} electrons have transferred from wool to polythene, as polythene acquires negative charge
(b) Yes, mass of 1.875 × 101210^{12} electrons
i.e., m = nmenm_e = 1.875 × 101210^{12} × 9.1 × 10−3110^{-31} kg
= 1.71 × 10−1810^{-18} kg has transferred from wool to polythene
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