Question

What will be the number of electrons passing through a heater wire in one $\text{minute}$, if it carries a current of $8\text{A}$?

• A. $3\times {10}^{21}$
• B. $3\times {10}^{28}$
• C. $3\times {10}^{30}$
• D. $3\times {10}^{12}$

Answer 1

The correct option is A $3\times {10}^{21}$

If $n$ number of electrons passes through a cross- section in $t\text{seconds}$ then, total charge passing in $t\text{seconds}$ will be $ne$.

And we know that

Current, $I=\frac{q}{t}=\frac{ne}{t}$

$\Rightarrow n=\frac{It}{e}=\frac{8\times 60}{1.6\times {10}^{-19}}$

$\therefore n=3\times {10}^{21}$ electrons

Hence, option $\left(a\right)$ is correct.

Key takeaway - electric current through an area is the rate of transfer of charge from one side of the area to the other.