A current of

Question:

A current of $10 \mathrm{~A}$ exists in a wire of crosssectional area of $5 \mathrm{~mm}^{2}$ with a drift velocity of $2 \times 10^{-3} \mathrm{~ms}^{-1}$. The number of free electrons in each cubic meter of the wire is

  1. $2 \times 10^{6}$

  2. $625 \times 10^{25}$

  3. $2 \times 10^{25}$

  4. $1 \times 10^{23}$


Correct Option: , 2

Solution:

$\mathrm{i}=10 \mathrm{~A}, \mathrm{~A}=5 \mathrm{~mm}^{2}=5 \times 10^{-6} \mathrm{~m}^{2}$

and $v_{d}=2 \times 10^{-3} \mathrm{~m} / \mathrm{s}$

We know, $\quad \mathrm{i}=$ neAvd

$\therefore 10=\mathrm{n} \times 1.6 \times 10^{-19} \times 5 \times 10^{-6} \times 2 \times 10^{-3}$

$\Rightarrow \mathrm{n}=0.625 \times 10^{28}=625 \times 10^{25}$

Leave a comment

Close

Click here to get exam-ready with eSaral

For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.

Download Now