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# A polythene piece rubbed with wool is found to have a negative charge of $3.2 × 10–7\; C.$ Estimate the number of electrons transferred.

$\begin{array}{1 1}(A)\;2 \times 10^9 \\(B)\;2 \times 10^{12} \\(C)\;2 \times 10^{15} \\(D)\;2 \times 10^8 \end{array}$

$Q = 3.2 × 10–7\; C$
$e = 1.6 × 10–19\; C$
Number of electron transferred,
$n=\large\frac{Q}{e}$
$\quad=\large\frac{3.2 \times 10^{-7}}{1.6 \times 10^{-19}}$$=2 \times 10^{12}$
Hence B is the correct answer.