$A$ wire of cross-sectional radius $r$ carries a current $I$ due to free electrons moving with a drift velocity $V$. What will be the current in another wire of the same material having half the radius and a drift velocity of $2V$?

Derive the relation between drift velocity and current density.

$A$ cylindrical resistor is connected across a battery $\varepsilon$. The cylinder has a uniform free electron density, and the middle part of the cylinder has a larger radius as shown in the figure. Which of the following graphs represents the variation of $V_d$ (drift velocity) with respect to $x$ (distance along the length of the resistor)?

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

$A$ beam contains $2 \times 10^8$ doubly charged positive ions per cubic centimeter,all of which are moving with a speed of $10^5 \,m/s$. The current density is ............. $A/m^2$.

$A$ conducting wire of cross-sectional area $1 \,cm^2$ has $3 \times 10^{23}$ charge carriers per $m^3$. If the wire carries a current of $24 \,mA$, then the drift velocity of the carriers is: