Question

Question 31
What is electrical resistivity of a material? What is its unit? Describe an experiment to study the factors on which the resistance of conducting wire depends.

Answer 1

Electrical resistivity (also known as resistivity, specific electrical resistance, or volume resistivity) is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. Resistivity is commonly represented by the Greek letter $\rho$ (rho). The SI unit of electrical resistivity is the ohm metre ($\Omega$ m) although other units like ohm centimetre ($\Omega$cm) are also in use. Many resistors and conductors have a uniform cross section with a uniform flow of electric current and are made of one material. In this case, the electrical resistivity $\rho$ is defined as:
$\rho =R\frac{A}{l}$
Where,
R is the electrical resistance of a uniform specimen of the material
l is the length of the piece of material
A is the cross - sectional area of the specimen. If A and l are given values of unity, it is seen that p is numerically equal to the resistance of a conductor having unit cross section and unit length. If R is in ohms, A in square centimeters, and l in centimeters, then $\rho$ is in ohm-centimeters.