Question

Ten million electrons pass from point $P$ to point $Q$ in one micro second. The current and its direction is

• A. $1.6 \times 10^{-14}\, A$, from point $P$ to point $Q$
• B. $3.2 \times 10^{-14} \,A$, from point $P$ to point $Q$
• C. $1.6 \times 10^{-6} \,A$, from point $Q$ to point $P$
• D. $3.2 \times 10^{-12} \,A$, from point $Q$ to point $P$

Answer 1

Answer: (C)

Here, number of electron, $n = 10000000 = 10^7$
Total charge on ten million electrons is
$Q = ne$ [where $e = 1.6 \times 10^{-19}C$]
$=10^{7} \times 1.6 \times10^{-19}\,C=1.6 \times10^{-12}\,C$
Time taken by ten million electrons to pass from point $P$ to point $Q$ is $t=1\,\mu s=10^{-6}\,s$
The current
$I=\frac{Q}{t}=\frac{1.6 \times10^{-12}}{10^{-6}}$
$=1.6 \times 10^{-6}\,A$
Since the direction of the current is always opposite to the direction of flow of electrons. Therefore due to flow of electrons from point $P$ to point $Q$ the current will flow from point $Q$ to point $P$.