Question

Calculate the number of electrons that constitute one coulomb of charge.

• A. $120\times {10}^{14}$ electrons
• B. $625\times {10}^{16}$ electrons
• C. $500\times {10}^{15}$ electrons
• D. $425\times {10}^{16}$ electrons

Answer 1

The correct option is B $625\times {10}^{16}$ electrons

Given that,
Amount of charge, $q=1\text{C}$
Charge of one electron, $e=1.6\times {10}^{-19}$
Let the number of electron which makes on the coulomb of charge is $n$
$\Rightarrow q=ne$
or, $1\text{C}=n(1.6\times {10}^{-19}C)$
$\Rightarrow n=\frac{1}{1.6\times {10}^{-19}}=0.625\times {10}^{19}$
$\therefore n=625\times {10}^{16}$

$\begin{array}{c}\text{Why this question ?}\\ \text{Tip: Total charge is always integral multiple of}\\ \text{charge of 1 electron.}\end{array}$