Define mobility and write its $SI$ unit.

Consider a wire carrying a current of $10\,A$ with a cross-sectional area of $1\,cm^2$. If the number of electrons per unit volume is $9 \times 10^{28}\,m^{-3}$,find the drift velocity of the electrons.

The mechanism of the heat produced in a conductor when an electric current flows through it can be explained on the basis of

$A$ potential difference is applied across the ends of a metallic wire. If the potential difference is doubled,then the drift velocity

Two cylindrical rods of uniform cross-sectional area $A$ and $2A$,having free electrons per unit volume $2n$ and $n$ respectively,are joined in series. $A$ current $I$ flows through them in a steady state. Then the ratio of the drift velocity of free electrons in the left rod to the drift velocity of electrons in the right rod is $\left( \frac{v_L}{v_R} \right)$.

If the ratio of the radii of two wires of the same material is $1 : 2$ and the ratio of the current flowing through them is $4 : 1$,what is the ratio of their drift velocities?