$A$ copper wire of length $10 \, m$ and radius $(10^{-2} / \sqrt{\pi}) \, m$ has an electrical resistance of $10 \, \Omega$. The current density in the wire for an electric field strength of $10 \, V/m$ is:

$A$ current passes through a wire of nonuniform cross-section. Which of the following quantities are independent of the cross-section?

$A$. The drift velocity of electrons decreases with the increase in the temperature of a conductor.
$B$. The drift velocity is inversely proportional to the area of cross-section of a given conductor.
$C$. The drift velocity does not depend on the applied potential difference to the conductor.
$D$. The drift velocity of an electron is inversely proportional to the length of the conductor.
$E$. The drift velocity increases with the increase in the temperature of a conductor.
Choose the correct answer from the options given below:

$A$ constant potential difference is applied between the ends of a wire. If the length of the wire is elongated to $4$ times its original length,then the drift velocity of electrons will be:

When there is an electric current through a conducting wire along its length,then an electric field must exist

$A$ charged particle is moving in an electric field of $3 \times 10^{-10} \text{ Vm}^{-1}$ with mobility $2.5 \times 10^6 \text{ m}^2 \text{V}^{-1} \text{s}^{-1}$. Its drift velocity is: