Question

Answer the following question:
Find the expression for the resistivity of a material.

Answer 1

Resistance R of a conductor depends on the length 'l' and area of cross-section 'A' of the conductor.

R α l

and R α  `(1)/("A")`

∴ `"R" ∝ "l"/"A"`,

∴ R = `"Q" xx ("l")/("A")` ( Q is  constant) 

Q ( Resistivity) = `("RA")/("l")`

Where Q (rho) is called resistivity of the conductor it is also called as specific resistance.
If we put L = 1m and A = 1m² then R = Q

Conclusion
Thus, the resistivity of a conductor is defined as the resistance of a conductor of unit length and unit area of cross-section. The SI units of resistivity are ohm-meter ( Ω - m).

Resistivity is the characteristics property of a material. It is a different material.