How to calculate resistivity of a material?

Question

To find a resistivity of material we are using
p=RA/l (ohm-meter)
p=rho,
R=resistence of material.
l =length of a material
A=cross sectional area of material.

my question is how ohm-meter comes as final answer. because length we can mention as meter, but, cross section area of a round material will be other than meter square.
please advice me how the answer come(ohm-meter) like this.

Answer 1

It's dimensionally consistent.
p = RA/l
R in Ω, A in m^2, l in m, p in Ω-m
Ω * m^2 / m = Ω-m
For a round wire you scale A by pi*r^2/D^2 (D=diameter) or pi/4. This scale factor is the area ratio of an inscribed circle to a square. It is dimensionless, so A is still in the same units, m^2.
Your email expressed doubt about, I think, dimensional consistency. Look at it this way. The value of p is the resistance of a unit cube of the material, i.e. a 1-m cube. If you reduce its conducting area measured perpendicular to the current flow you increase its resistance proportionally. Similarly if you increase its length in the direction of current flow you increase its resistance proportionally. That's what the equation (in the form R = pl/A) represents.
A similar system of expressing conductivity is based on Ω-cm units. The resistance of a 1-cm cube is 100 * the resistance of a 1-m cube of the same material, because l is scaled by 0.01 and A is scaled by 0.0001. So the Ω-cm value of a given material is 100 * the Ω-m value.

Answer 2

Calculate Resistivity

Answer 3

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RE:
How to calculate resistivity of a material?
To find a resistivity of material we are using
p=RA/l (ohm-meter)
p=rho,
R=resistence of material.
l =length of a material
A=cross sectional area of material.

my question is how ohm-meter comes as final answer. because length we can mention as meter, but, cross section area of a round...

Answer 4

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ρ = R * A / l ρ = (2) * (1.26 x 10^-7) / 0.1 ρ = 2.51 x 10^-6 Ω*m where R is resistance, A is the cross-sectional area of the wire in meters^2 and l is the length of the wire in meters.

Answer 5

By R = rho x L/A =>2 = rho x 0.1/[(pi/4) x d^2] =>rho = 20 x (3.14/4) x (0.4 x 10^-3)^2 =>rho = 2.51 x 10^-6 ohm-m

Answer 6

Your doubt is genuine. We are considering the area of cross section as UNIT SQUARE.