Question

A connecting wire as shown in figure carries a current of $0.5A$. Observe the cross-section at A-B for $20s$. How many electrons would pass through this cross-section in $20s$?

• A. $62.5\times {10}^{19}$
• B. $6.25\times {10}^{19}$
• C. $6.05\times {10}^{19}$
• D. $60.5\times {10}^{19}$

Answer 1

The correct option is B $6.25\times {10}^{19}$

Given,
Electric Current, $I=0.5A$
Time, $t=20s$

Let Q be the amount of charge flowing through the cross section. From definition of electric current,
$I=\frac{Q}{t}$
$Q=It$
$Q=0.5A\times 20s=10C$

Magnitude of charge of an electron, $e=1.6\times {10}^{-19}C$
Number of electrons,
$n=\frac{Q}{e}$
$n=\frac{10C}{1.6\times {10}^{-19}C}$
$n=6.25\times {10}^{19}$