State the laws of resistance of a conductor. Define specific resistance of material of a conductor. Mention the SI unit of specific resistance.

Explanation

Resistance .R. of a conductor is,
(i) directly proportional to the length of the conductor.
(ii) inversely proportional to the area of cross-section of the conductor.
i.e., `RpropL/A` or `R=(pL)/A`
where, .p. is the resistivity or specific resistance of the conductor.
For one metre cube of the material,L = 1 m,A = `1m^(2)` hence R = p.
Specific resistance of material of the conductor may be defined as numerically equal to the resistance of the material taken in the form of a cube of side one metre.
The SIU of specific resistance is `.Omegam.`. Specific resistance is different for different materials and hence it is an unique physical quantity.