When a potential difference is applied across the ends of a linear metallic conductor,

The drift velocity of the electrons in a copper wire of length $2\ m$ under the application of a potential difference of $200\ V$ is $0.5\ m/s$. Their mobility (in $m^2 V^{-1} s^{-1}$) is

$A$ cylindrical conductor of diameter $0.1 \text{ mm}$ carries a current of $90 \text{ mA}$. The current density (in $\text{Am}^{-2}$) is (take $\pi \simeq 3$):

Consider a metallic cube of edge length $L$. Its resistance,$R$,measured across its opposite faces is $R = \frac{m_e v}{n e^2 L^2}$,where $n$ is the number density and $v$ is the drift speed of electrons in the cube,and $e$ and $m_e$ are the charge and mass of an electron respectively. Assuming the de-Broglie wavelength of the electron to be $L$,the maximum resistance of the sample is closest to ............. $\Omega$ ($e = 1.60 \times 10^{-19} \, C$; $m_e = 9.11 \times 10^{-31} \, kg$; Planck's constant,$h = 6.63 \times 10^{-34} \, Js$)

Every atom contributes one free electron in copper. If $1.1 \ A$ current is flowing in a copper wire having a $1 \ mm$ diameter,then the drift velocity (approx.) will be (Density of copper $= 9 \times 10^3 \ kg \ m^{-3}$ and atomic weight $= 63$).

$A$ 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: