R
l
a
ρ
( )
where
ρ the resistivity constant for the material m)
l the length the material (m)
a the cross-sectional area the material (m2
).
The resistivity (symbol the Greek letter ‘rho’) material defined
as the resistance sample unit length and unit cross-section.0 109
.
V R
V
12
A V
Resistivity
The resistance opposition current flow varies for different materials,
each having particular constant value.
Example 2
The insulation resistance measured between phase conductors 400 supply was found
to 2MΩ.Basic electrotechnical units and theory
83
∴
230
4
57 5
V
A
. Using the constants for particular material
we can calculate the resistance any length and thickness that material
from the equation.3.
Table 4.0 109
Iron 100.5 109
Brass 75.c. Calculate the supply voltage.4 109
Copper 17. know the resistance of, say,
1m material, then the resistance will five times the resistance
of 1m.3 Resistivity Values
Material Resistivity m)
Silver 16. supply, current
of flowed. Typical
values are given Table 4.5 109
Aluminium 28.
I
V
R
∴
400 V
2 10
200 200 A
6
6
Example 3
When resistor was connected across the terminals unknown d.
Definition
The resistivity (symbol the Greek
letter ‘rho’) material defined
as the resistance sample unit
length and unit cross-section. Calculate the leakage current
