V R
V
12
A V
Resistivity
The resistance opposition current flow varies for different materials,
each having particular constant value.5 109
Brass 75.3. Calculate the leakage current.
Example 2
The insulation resistance measured between phase conductors 400 supply was found
to 2MΩ.0 109
Iron 100. Typical
values are given Table 4.
Table 4.0 109
.4 109
Copper 17.c.
Definition
The resistivity (symbol the Greek
letter ‘rho’) material defined
as the resistance sample unit
length and unit cross-section. Using the constants for particular material
we can calculate the resistance any length and thickness that material
from the equation.3 Resistivity Values
Material Resistivity m)
Silver 16.
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
).Basic electrotechnical units and theory
83
∴
230
4
57 5
V
A
.
The resistivity (symbol the Greek letter ‘rho’) material defined
as the resistance sample unit length and unit cross-section.5 109
Aluminium 28. Calculate the supply voltage.
I
V
R
∴
400 V
2 10
200 200 A
6
6
Example 3
When resistor was connected across the terminals unknown d. know the resistance of, say,
1m material, then the resistance will five times the resistance
of 1m. supply, current
of flowed
