Question

The number of electrons moving per second through the filament of a lamp of $100W$, operating at $200V$ is

• A. $3.1\times 10^{18}$
• B. $3.1\times 10^{19}$
• C. $4.8\times 10^{18}$
• D. $4.8\times 10^{19}$

Answer 1

Answer: (A)

$P=Vi\Rightarrow i=\frac{P}{V}=\frac{100}{200}=0.5A$
Charge passing through the lamp in $1s$
$q=i\times t=0.5\times 1=0.5C(\because t=1s)$
Therefore, number of electrons moving through the filament per second
$N=q/e=\frac{0.5}{1.6\times 10^{-19}}=3.125\times 10^{18}$