5 109
Aluminium 28.3. 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
. supply, current
of flowed.
V R
V
12
A V
Resistivity
The resistance opposition current flow varies for different materials,
each having particular constant value.0 109
Iron 100. Calculate the supply voltage.4 109
Copper 17.3 Resistivity Values
Material Resistivity m)
Silver 16. Typical
values are given Table 4.
Example 2
The insulation resistance measured between phase conductors 400 supply was found
to 2MΩ. know the resistance of, say,
1m material, then the resistance will five times the resistance
of 1m.
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
).c.
Definition
The resistivity (symbol the Greek
letter ‘rho’) material defined
as the resistance sample unit
length and unit cross-section.
The resistivity (symbol the Greek letter ‘rho’) material defined
as the resistance sample unit length and unit cross-section.0 109
.
Table 4. Calculate the leakage current.5 109
Brass 75.
I
V
R
∴
400 V
2 10
200 200 A
6
6
Example 3
When resistor was connected across the terminals unknown d
