c.
Example 2
The insulation resistance measured between phase conductors 400 supply was found
to 2MΩ. supply, current
of flowed. Using the constants for particular material
we can calculate the resistance any length and thickness that material
from the equation.Basic electrotechnical units and theory
83
∴
230
4
57 5
V
A
.5 109
Aluminium 28.3.0 109
.3 Resistivity Values
Material Resistivity m)
Silver 16.
Definition
The resistivity (symbol the Greek
letter ‘rho’) material defined
as the resistance sample unit
length and unit cross-section. Calculate the leakage current.4 109
Copper 17.
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
). Typical
values are given Table 4.
I
V
R
∴
400 V
2 10
200 200 A
6
6
Example 3
When resistor was connected across the terminals unknown d. Calculate the supply voltage.
The resistivity (symbol the Greek letter ‘rho’) material defined
as the resistance sample unit length and unit cross-section.5 109
Brass 75.
Table 4.0 109
Iron 100. know the resistance of, say,
1m material, then the resistance will five times the resistance
of 1m.
V R
V
12
A V
Resistivity
The resistance opposition current flow varies for different materials,
each having particular constant value
