Question

What is meant by electrical resistivity of a material? Derive its S.I. unit. Describe an experiment to study the factor on which the resistance of a conducting wire depends.

Answer 1

We know that Resistance depends on voltage and current but it also depends on the nature of a conductor this phoenomen is called resistivity.

Measure the resistance of a conductor at a given voltage and current now keeping V & I constant change it's length and area of cross section then measure it's new resistance & you will find that

R is directly proportional to l

R is inversely proportional to A

Therefore R is directly proportional to l/A

R = pl/A

p(rho) = RA/l

p(Resistivity) = ohm × (metre)^2 / metre

p = ohm metre

:-)