Drift of Electrons and the Origin of Resistivity

Two conducting wires X and Y of same diameter but different materials are joined in series across a battery. If the number density of electrons in X is twice that in Y, find the ratio of drift velocity of electrons in the two wires would be:

The current of a conductor flowing through a conductor in terms of the drift speed of electrons is (the symbols have their usual meanings) 

Derive an expression for the resistivity of a good conductor, in terms of the relaxation time of electrons.

Two metallic wires of the same material have the same length but cross-sectional area is in the ratio $1:2$. They are connected (i) in series and (ii) in parallel. Compare the drift velocities of electrons in the two wires in both the cases (i) and (ii).

The relation between current and drift velocity is

Two statements are given-one labelled Assertion (A) and the other labelled Reason (R).

Select the correct answer to these questions from the codes (A), (B), (C), and (D) as given below.

Assertion: As the temperature of a conducting wire increases, the drift velocity of the electrons also increases.

Reason: With an increase in temperature, the average time of collision increases.

Average time between successive collisions for an electron for a conductor under a certain potential difference is 2 × 10-14 s. The mobility of electron in metal conductor is (mass of electron = 9.1 × 10-31 kg)

In a wire of cross-section radius r, free electrons travel with drift velocity v when a current I flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is 2V?

The average time between successive collisions for an electron for a conductor potential difference is $2\times {10}^{-14} \mathrm{s}$. The mobility of electrons in metal conductors. (mass of the electron$=9.1\times {10}^{-31} \mathrm{kg}$ ) 

Suppose a current carrying wire has a cross sectional area that, gradually become smaller along the wire, has the shape of a very long cone as shown in figure. Choose the correct statement:

A charged particle is moving in an electric field of $3\times {10}^{-10} \mathrm{V} {\mathrm{m}}^{-1}$ with mobility $2.5\times {10}^6 {\mathrm{m}}^2 {\mathrm{V}}^{-1} {\mathrm{s}}^{-1}$, its drift velocity is

(a) Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area $1.0\times {10}^{-7} {\mathrm{m}}^2$ carrying a current of  $1.5 \mathrm{A}$. Assume that each copper atom contributes roughly one conduction electron. The density of copper is $9.0\times {10}^3 \mathrm{kg}/{\mathrm{m}}^3$, and its atomic mass is $63.5 \mathrm{u}$. (b) Compare the drift speed obtained above with, (i) thermal speeds of copper atoms at ordinary temperatures,  (ii) speed of propagation of electric field along the conductor which causes the drift motion.

An electron takes $40\times {10}^3 \mathrm{s}$ to drift from one end of a metal wire of length $2 \mathrm{m}$ to its other end. The area of cross-section of the wire is $4 {\mathrm{mm}}^2$ and it is carrying a current of $1.6 \mathrm{A}$. The number density of free electrons in the metal wire is

An electron starts moving in a uniform electric field of strength $E=10 \mathrm{kV} {\mathrm{cm}}^{-1}$. How soon after the start will the kinetic energy of the electron become equal to its rest energy?

Find the time to move electron from A to B if $i= 0.8 \mathrm{A}$ and $n= {10}^{28}/{\mathrm{m}}^3$.

A current of $0.1 \mathrm{A}$ though wire of cross-section area $1 {\mathrm{mm}}^2$. Find drift velocity of free electron if the free electron density $100 {\mathrm{m}}^{-3}$.

A. The drift velocity of electrons decreases with the increase in the temperature of conductor.
B. The drift velocity is inversely proportional to the area of cross-section of given conductor.
C. The drift velocity does not depend on the applied potential difference to the conductor.
D. The drift velocity of electron is inversely proportional to the length of the conductor.
E. The drift velocity increases with the increase in the temperature of conductor.

Choose the correct answer from the options given below:

Define mobility.