Electrical resistivity of a conductor is a measure of the resisting power of a specified material to the passage of an electric current. It is a constant for a given material.

**ELECTRICAL RESISTIVITY
ELECTRICAL CONDUCTIVITY**

You can verify by doing
an experiment that the resistance of any conductor ‘R’ is directly proportional
to the length of the conductor ‘L’ and is inversely proportional to its area of
cross section ‘A’.

Where, *ρ* (rho) is
a constant, called as electrical resistivity or specific resistance of the
material of the conductor.

From equation (4.4), ρ = RA/L

If L = 1 m, A = 1 m^{2}
then, from the above equation *ρ* = R

Hence, the electrical
resistivity of a material is *defined as the resistance of a*** conductor
of unit length and unit area of cross section**. Its unit is

Electrical resistivity
of a conductor is a measure of the resisting power of a specified material to
the passage of an electric current. It is a constant for a given material.

Conductance of a
material is the property of a material to aid the flow of charges and hence,
the passage of current in it. The conductance of a material is mathematically ** defined
as the reciprocal of its resistance **(R).

G = 1/R (4.5)

Its unit is ohm^{–1}.
It is also represented as ‘mho’.

** The reciprocal of
electrical resistivity of a material is called its electrical conductivity**.

Its unit is ohm^{–1}
metre^{–1} . It is also represented as mho metre^{–1}. The
conductivity is a constant for a given material. Electrical conductivity of a
conductor is a measure of its ability to pass the current through it. Some
materials are good conductors of electric current. Example: copper, aluminium,
etc. While some other materials are non-conductors of electric current
(insulators). Example: glass, wood, rubber, etc.

Conductivity is more for
conductors than for insulators. But, the resistivity is less for conductors
than for insulators. The resistivity of some commonly used materials is given
in Table 4.2.

The resistance of a wire
of length 10 m is 2 ohm. If the area of cross section of the wire is 2 × 10^{–7}
m^{2}, determine its (i) resistivity conductance and (iii) conductivity

Given: Length, L = 10 m,
Resistance, R = 2 ohm and Area, A = 2 × 10^{–7} m^{2}

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10th Science : Chapter 4 : Electricity : Electrical Resistivity Electrical Conductivity | Definition, Formula, Solved Example Problems

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