Question

A copper wire of radius $0.1mm$ and resistance $2k\Omega$ is connected across a power supply of $40V$. The number of electrons transferred per second between the supply and the wire at one end is

• A. $2.00\times 10^{16}$
• B. $1.25\times 10^{17}$
• C. $2.85\times 10^{17}$
• D. $3.25\times 10^{16}$

Answer 1

Answer: (B)

Radius of copper wire, $r=0.1mm$
$=1\times 10^{-4}m$
Resistance, $R=2k\Omega =2\times 10^3\Omega$
Power supply, $V=40V$
Current flowing through the wire,
$I=\frac{V}{R}=\frac{40}{2\times 10^3}=2\times 10^{-2}A$
$\therefore$ Charge flowing per second
$q=It=2\times 10^{-2}\times 1=2\times 10^{-2}C$
$\therefore$ Number of electrons transferred,
$n=\frac{q}{e}=\frac{2\times 10^{-2}}{1.6\times 10^{-19}}$
$=1.25\times 10^{17}$ electrons