The number density of free electrons in copper is nearly $8 \times 10^{28} \ m^{-3}$. $A$ copper wire has an area of cross-section $= 2 \times 10^{-6} \ m^2$ and is carrying a current of $3.2 \ A$. The drift speed of the electrons is $..... \times 10^{-6} \ m \ s^{-1}$.

The drift velocity of free electrons in a conductor is $v$ when a current $i$ is flowing in it. If both the radius and current are doubled,then the drift velocity will be

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 $\left( \frac{v_L}{v_R} \right)$.

$A$ uniform copper wire carries a current $i$ amperes and has $p$ carriers per meter$^3$. The length of the wire is $\lambda$ meters and its cross-section area is $s$ meter$^2$. If the charge on a carrier is $q$ coulombs,the drift velocity in $ms^{-1}$ is given by

$A$ 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)?

An electric cell of emf $E$ is connected across a copper wire of diameter $d$ and length $l$. The drift velocity of electrons in the wire is $v_{d}$. If the length of the wire is changed to $2l$,the new drift velocity of electrons in the copper wire will be