Question

A conductor carries a current of 0.2 A. How many electrons will flow in 30 seconds if the charge on one electron is $1.6\times {10}^{-19}C$.

• A. $3\times {10}^{19}$
• B. $3.75\times {10}^{19}$
• C. $2.75\times {10}^{19}$
• D. $2\times {10}^{19}$

Answer 1

The correct option is B

$3.75\times {10}^{19}$

It is given that current $I=0.2A$, time $t=30s$ and charge on one electron is $e=1.6\times {10}^{-19}C$.

Let the number of electrons be $n$.

We know $I=\frac{Q}{t}$ and $Q=n\times \text{e}$ where $e$ is the charge on one electron.

So, $I=\frac{n\times e}{t}$

On substituting the values, $0.2=\frac{n\times 1.6\times {10}^{-19}}{30}$

$\Rightarrow n=3.75\times {10}^{19}$

Therefore, $3.75\times {10}^{19}$ electrons will flow in 30 seconds.