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

Assume a hypothetical wire in which free electron density changes with temperature in proportionality $n \propto T$,assuming $\tau$ (relaxation time of collision) and dimensions of the wire remain unchanged with increasing temperature. Which one of the resistance $v/s$ temperature graphs is true?

Is the motion of a charge across a junction momentum conserving? Why or why not?

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 $..... \times 10^{-6} \ m \ s^{-1}$.

An ionization chamber with parallel conducting plates as anode and cathode has $5 \times 10^7$ electrons and the same number of singly-charged positive ions per $cm^3$. The electrons are moving at $0.4\, m/s$. The current density from anode to cathode is $4\,\mu A/m^2$. The velocity of positive ions moving towards cathode is ............. $m/s$. [$AIPMT$ $1992$]

$A$ conductor of non-uniform cross-section is connected to a source of constant potential difference as shown in the figure. Then: