Two wires $A$ and $B$ of the same material,having radii in the ratio $1: 2$,carry currents in the ratio $4: 1$. The ratio of drift speed of electrons in $A$ and $B$ is .......

When current flows through a conductor,then the order of drift velocity of electrons will be

The current density in a cylindrical wire of radius $4 \; mm$ is $4 \times 10^{6} \; A \cdot m^{-2}$. The current through the outer portion of the wire between radial distance $\frac{R}{2}$ and $R$ is $\dots \; \pi \; A$.

The relationship between the electric field $E$ and the current density $J$ is given by:

Why is current not formed in solid conductors in the absence of an electric field?

$A$ current of $5\, A$ passes through a copper conductor (resistivity $= 1.7 \times 10^{-8}\, \Omega \, m$) of radius of cross-section $5\, mm$. Find the mobility of the charges if their drift velocity is $1.1 \times 10^{-3}\, m/s$.