The resistivity of a material, (units Ohm metre, symbol
) is it's ability to resist the passage of an electric current. Resistance is measured in Ohms (symbol
) and resistance defined as the resistance between the faces of a cubic metre block of material, or more practically, calculated from the equation
where
is the length of the material along which the current passes and
is the constant cross sectional area. Some resistivities for various materials are given below.
All values at 20 °C.
|
Material |
Resistivity (Ohm metre) |
|---|---|
|
Aluminium |
|
|
Carbon |
|
|
Copper |
|
|
Germanium |
.46 |
|
Glass |
|
|
Gold |
|
|
Hard Rubber |
about |
|
Iron |
|
|
Lead |
|
|
Nichrome |
|
|
Platinum |
|
|
Quartz (Fused) |
|
|
Silicon |
|
|
Silver |
|
|
Sulphur |
|
|
Tungsten |
|
to
The conductivity of a material (units
symbol
)is it's ability to conduct electricity and is defined as
The conductivity of Germanium is