When a piece of polythene is rubbed with wool, a negative charge of $4 \times 10^{-7} \mathrm{C}$ is…

When a piece of polythene is rubbed with wool, a negative charge of $4 \times 10^{-7} \mathrm{C}$ is developed on the polythene. The number of electrons transferred wool to polythene is $\left[\mathrm{e}=1.6 \times 10^{-19} \mathrm{C}\right]$
  1. $1.5 \times 10^{12}$
  2. $3.5 \times 10^{13}$
  3. $2.5 \times 10^{13}$
  4. $2.5 \times 10^{12}$

Solution

$\begin{aligned} & \mathrm{q}=4 \times 10^{-7} \\ & \mathrm{q}=\mathrm{Ne} \\ & \mathrm{N}=\frac{\mathrm{q}}{\mathrm{e}}=\frac{4 \times 10^{-7}}{1.6 \times 10^{-19}}=2.5 \times 10^{12}\end{aligned}$ ^

Asked in: MHT CET 2021 (21 Sep Shift 2)

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