Question

If ${10}^6$ electrons per second are flowing through an area of cross section of ${10}^{-4}$ $m^2$ then the current will be:-

• A. $1.6\times {10}^{-7}$ $A$
• B. $1.6\times {10}^{-13}A$
• C. $1\times {10}^{-6}A$
• D. $1\times {10}^{2}A$

Answer 1

The correct option is B $1.6\times {10}^{-13}A$

$\text{Step 1: Charge flow in one second}$

No. of electron flowing per second $n={10}^6$

Amount of charge flowing per second

$Q=ne={10}^6\times 1.6\times {10}^{-19}C=1.6\times {10}^{-13}C$

$\text{Step 2: Current}$

Current is amount of charge flowing per second

$I=Q/t=\frac{1.6\times {10}^{-13}C}{1sec}$$=1.6\times {10}^{-13}A$

Hence, Option B is correct.

$\text{[Note:}$ In this problem there is no use of Area of cross section, it has been given just for confusing the students. If current density $J(=\frac{I}{A})$ had been asked, then we would have used the Area $\text{]}$