Example 2
The insulation resistance measured between phase conductors 400 supply was found
to 2MΩ.
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.
V R
V
12
A V
Resistivity
The resistance opposition current flow varies for different materials,
each having particular constant value.Basic electrotechnical units and theory
83
∴
230
4
57 5
V
A
.
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
). Using the constants for particular material
we can calculate the resistance any length and thickness that material
from the equation.5 109
Aluminium 28. Typical
values are given Table 4.
The resistivity (symbol the Greek letter ‘rho’) material defined
as the resistance sample unit length and unit cross-section.
Table 4.3.0 109
Iron 100. Calculate the leakage current.3 Resistivity Values
Material Resistivity m)
Silver 16.4 109
Copper 17. Calculate the supply voltage. know the resistance of, say,
1m material, then the resistance will five times the resistance
of 1m.0 109
.5 109
Brass 75.c. supply, current
of flowed
