Question

Write expression for resistivity,conductivity and relaxation time

Answer 1

Resistivity : At a given temperature , the resistance (R) of a conductor depends on its length (L),area of cross section (A) and the material it is made of .

If the resistance of a conductor is R,then

R alpha L
Also, R alpha 1/A

:. R alpha L / A

R = p L/A

p is the constant of proportionality and is called the resistivity of the material.The unit of resistivity in SI units is Ohm meter.
Resistivity is a specific property of a material and different materials have different resistivity.

Conductivity : The electrons start moving from to and to the end at lower potential to the end at higher potential.This directional motion of the electrons cause the flow of current.Moving electrons strike the atoms and ions which lie along their path.Such collision cause hindrance to the flow of electrons and oppose the current.This hindrance is called the resistance of the conductor.



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Answer 2

Answer:

Resistivity commonly symbolized by the greek letter rho, Pis quantitatively equal to the resistance R of a specimen such as a wire, multiplied by its cross-sectional area A, and divided by its length I ; P = RA/I. The unit of resistance is the ohm

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