When a long straight uniform rod is connected across an ideal cell, the drift velocity of electrons in it is…
When a long straight uniform rod is connected across an ideal cell, the drift velocity of electrons in it is $v$. If a uniform hole is made along the axis of the rod and the same battery is used, then the drift velocity of electrons becomes
$v$
$>v$
$ < v$
$zero$
Solution
The drift velocity,
$\begin{aligned}
& v_a=\frac{1}{n e A}=\frac{V}{n e A}\left(\because l=\frac{V}{R}\right) \\
& \therefore v_d=\frac{V}{\rho \frac{l}{A} n e A}\left(\because R=\rho \frac{l}{A}\right) \\
& \therefore v_d=\frac{V}{\rho l n e}
\end{aligned}$
As drift velocity is independent of cross-sectional area (A) so no change in drift velocity.