Electrical conductivity
Table of Contents
Electrical conductivity
is a measure of how well a material accommodates the transport of electric charge. Its
SI derived unit
is the
siemens
per
metre
, (
A
2
s
3
m
-3
kg
-1
) (named after
Werner von Siemens
).
Electrical conduction
is an
electrical phenomenon
where a material (
solid
or otherwise) contains movable particles with
electric charge
, which can carry
electricity
. When a difference of electrical potential is placed across a conductor, its movable charges flow, and an
electric current
appears. Conductivity is defined as the ratio of the
current density
to the
electric field
strength. It is the
reciprocal
of
electrical resistivity
.
Electrical conductivity may be represented by the
Greek letters
κ
,
Ï
or
γ
.
Classification of materials by conductivity
Scientists often divide
material
s into three classes based upon their respective conductivities:
-
A
conductor
such as a
metal
has high conductivity.
-
An
insulator
like
glass
or a
vacuum
has low conductivity.
-
The conductivity of a
semiconductor
is generally intermediate, but varies widely under different conditions, such as exposure of the material to electric fields or certain frequencies of
light
.
Some typical electrical conductivities
-
Silver
: 78 · 10
6
S/m (7 800 000 S/cm; highest electrical conductivity of any metal)
-
Sea water: 5 S/m
-
Drinking water: 0.005 â 0.05 S/m
-
Ultra pure water: 5.5 · 10
-6
S/m
See also