microscopic form of ohms law

3 years ago

Share

Answers : (1)

                                        

Dear Harpreet Singh,


Ohm's Law is the linear proportionality between current and voltage that occurs for most conductors of electricity. A graph of voltage against current is a straight line. The gradient is the resistance.


The most well known form of Ohm's law is V=IR, where V is the voltage, I is the current and R is the resistance. However there is another form of Ohm's law which often used by physicists that operates on a microscopic level, relating the current density J to the conductivity σ and the electric field, E.


To see how consider, the volume of material with faces of area A a distance l apart. With an e.m.f. V across the faces of the material



  • the current is proportional to the voltage V

  • the current is proportional to the surface area A

  • and the current is inversely proportional to the distance l.


The current is therefore,


I = VAσ/l.


R = l/Aσ


The proportionality constant σ is the conductivity of the material.


V/l = |E|, and J = I/A in the direction of E so in general we have the constitutive relation.


J = σE


 


                      Good Luck!!!!!!


 


 Plz. approve my answer, if you loved it, by clicking 'Yes' given below!!!!!!Plz. Plz. Plz.!!!!!!! Don't forget!!!!!!!!Smile

3 years ago

Post Your Answer

More Questions On Electric Current

Ask Experts

Have any Question? Ask Experts
Post Question
 
Answer ‘n’ Earn
Attractive Gift
Vouchers
To Win!!!
Click Here for details
What is definition of electric current
 
 
the rate of flow of electric charges through any cross section of a conductor is called electric current.
 
king 7 months ago
Figure: http://s24.postimg.org/6jwbbnzlh/image.png The potential difference between A and B will be what? Ans. 12 V
 
 
let potential at middle junction be x. since the current coming out of two arms from point b is 3 A and 4A , by kirchoff`s 1st law, the current flowing between x and B is 7A. now moving from...
 
Revant Buch 4 months ago
Lighting a tunnel: A person walking through the tunnel turns a lamp in the first half of it and then he turns a second lamp for the second half of the tunnel and the first one is turned off....
 
 
Thanks & Regards, Nirmal Singh Askiitians faculty
  img
Nirmal Singh. 5 months ago
 
parallel connection of the two bulbs is the correct way
 
VISHAL GAUTAM 5 months ago
What is meant by Carrier signal ,? how to generate and add it to our considered signal ?
 
 
Carrier signal is signal with high frequency which is used coupled with a message signal of very low frequency for it to transmit to long distance. Arun Kumar IIT Delhi Askiitians Faculty
  img
Arun Kumar 3 months ago
why and when does spherical wavefront behave as plane wavefront?
 
 
Here every wavelet acts as a source of a secondary wavelet but at infinite distance it becomes planer because of disance btw source and wavelet becomes more.
 
srinu kummari 11 months ago
A tuning fork of frequency 480 Hz resonates with a tube closed at one end of length 16 cm and diameter 5 cm in fundamental mode. Calculate velocity of sound in air.
 
 
Hello Student, Please find the answer to your question KEY CONCEPT : In the fundamental mode (ℓ + 0.6r) = ℷ/4 = v/4f ⇒ v = 4f (ℓ + 0.6r) = 336 m/s. Thanks Jitender Pal askIITians...
  img
Jitender Pal 2 months ago
View all Questions »