Home
Class 12
PHYSICS
The mean free path of conduction elector...

The mean free path of conduction electorns in copper is about `4xx10^(-8)`m. for a copper block, find the electric field which can give, on an average, 1eV energy to a conduction electron.

Text Solution

Verified by Experts

Lets the electric field be E, The force on an electorn is eE. As the electron moves through a distance d, the work done on it is eEd. This is equal to the energy transferred to the electron. As the electron travels an average distance of `4xx10^(-8)`m before a collision ,the energy transferred is `eE(4xx10^(-8)m).to get 1eV energy form the electric field,
`eE(4xx10^(-8)m)=1eV`
or,E=2.5xx10(7)Vm^(-1).`
Doubtnut Promotions Banner Mobile Dark
|

Topper's Solved these Questions

  • SEMICONDUCTOR AND SEMICONDUCTOR DEVICES

    HC VERMA|Exercise Worked out examples|11 Videos

  • SEMICONDUCTOR AND SEMICONDUCTOR DEVICES

    HC VERMA|Exercise Question for short answer|10 Videos

  • PHOTOMETRY

    HC VERMA|Exercise All Questions|44 Videos

  • SPEED OF LIGHT

    HC VERMA|Exercise Exercises|3 Videos

Similar Questions

Explore conceptually related problems

Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 1.0xx10^(-7)m^(2) carrying a current of 1.5A . Assume the density of conduction electrons to be 9xx10^(28)m^(-3) .

(a) Esttimate the average drift speed of conduction electrons in a copper wite of cross-secttonal area 1.0 xx 10 ^(-7)m^(2) carrying a current of 1.5A. Assume the each copper atom contrbutes roughly one conduction electron. The density of copper is 9.0 xx 10 ^(3)kg//m^(3), and its atomic mass is 63.5 u. (b) Compare the drift speed obyained above with, (1) thermal speeds of copper atoms at ordinary temperaturtes. (ii) speed of propagation of electric field along the conductor which causes the drift motion.

Let (Delta)E denote the energy gap between the valence band and the conduction band.The population of conduction electrons (and of the holes)is roughly proportional to e^(-Delta E//2kT). Find the ratio of the concentration of conduction electrons in diamond to that in silicon at room tempareture 300K. (Delta E) for silicon is 1.1 ev and for diamond is 6.0eV.How many conduction electrons are likely to be in one cubic meter of diamond ?

A currrent I is passed through a silver strip of width d and area of cross section A. The number of free electrons per unit volume is n. (a) Find the drift velocity v of the electrons. (b) If a magnetic field B exists in the region as shown in what is the average magnetic force on the free electrons? (c) Due to the magnetic force, the free electrons get accumulated on one side of the conductor along its length. This produces a transverse electric field in the conductor which opposes the magnetic force on the electrons. Find the magnitude of the electric field which will be the potential diference developed across the width of the conductor due to the electron- accumulation? The appearance of a transverse emf, when a current-carrying wire is placed in a magnetic field, is called hall effect.

(a) In the above example, the electron drift speed is estimated to be only a few mm s^(-1) for currents in the range of a few amperes, How then is current established almost the instant a circuit is closed? (b)The electron drift arises due to the force experienced by electrons in the electric fieldinside the conductor. But force should cause acceleration. Why then do the electrons acquire a steady average drift speed? If the electron drift speed is so small, and the electron's charge is small, how can we still obtain large amounts of current in a conductor? (d)When electrons drift in a metal from lower to higher potential, does it mean that all the "free' electrons of the metal are moving in the same direction? (e) Are the paths of electrons straight lines between successive collisions (with the positive ions of the metal) in the (i) absence of electric field, (ii) presence of electric field?

Calculate the mean free path of air molecules at STP. The diameter of N_2 and O_2 is about 3xx10^(-10) m.

Calculate the mean free path of air molecules at STP. The diameter of N_2 and O_2 is about 3xx10^(-10) m.

A parallel plate capacitor is to be designed with a voltage rating 1kV, using a maeterial of dielectric constant 3 and dielectric strength about 10^(7) Vm^(-1) , (Dielectric strength is the maximum electric field a material can tolerate without breakdown, i.e, without starting to conduct electricity through partial ionisation.) For safety, we should like the field never to exceed say 10% of the dielectric strength. What minimum area of the plates is required to have a capacitance of 50pF?

In a p-n junction, the depletion region is 400nm wide and and electric field of 5xx10^5Vm_(-1) exists in it (a)Find the height of the potential barrier, (b)What should be the minimum kinetic energy of a conduction electron which can diffuse from the n-side to the p-side?

The density of electrons in copper is 8.4 xx 10^(22) per cm^(3) ? Calculate the drift velocity of electrons in a copper wire of 2 mm^(2) - area of cross section and carries a current of 0.15 A.

Home
Profile