Question

A conductor is carrying 0.4 amperes of current. How many free electrons have crossed through a given cross-section of the conductor in 40 seconds?

Answer 1

Step1:- Given data;

$current,i=0.4Ampere$

$Timetakenis,t=40sec$

[Note:- charge on one electron is $e=1.6\times {10}^{-19}coulomb$]

Step2:- Finding total charge flow

$charge\left(q\right)=i\times t=0.4\times 40=16C$

Step3:- Finding free electrons crossed through the given Cross-section of the conductor in 40 second

$q=n\times e$

Now, $$\begin{gathered} q=ne=16C \\ \Rightarrow n\times 1.6\times {10}^{-19}=16 \\ \Rightarrow n=\frac{16}{1.6\times {10}^{-19}}={10}^{20}electrons \end{gathered}$$

Hence, ${10}^{20}$electrons crossed through a given cross-section of a conductor in 40 seconds.