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NCERT Class XII Chapter
Electric Charges and Fields
Questions With Solutions

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Question : 11
Total: 34
A Polythene piece rubbed with wool is found to have a negative charge of 3 × 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?
Solution:  
(a) q = ne or n =
q
e
 =
3×10−7
1.6×10−19
 = 1.875 × 1012
so, 1.875 × 1012 electrons have transferred from wool to polythene, as polythene acquires negative charge
(b) Yes, mass of 1.875 × 1012 electrons
i.e., m = nme = 1.875 × 1012 × 9.1 × 10–31 kg
= 1.71 × 10–18 kg has transferred from wool to polythene
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