Resistance &
conductivity
The electrical resistance of a wire would be expected to be
greater for a longer wire, less for a wire of larger cross sectional area, and
would be expected to depend up on the material out of which the wire is made.
Experimentally, the dependence upon these properties is a straightforward one
for a wide range of conditions, and the resistance of a wire can be expressed
as
R=(ρL)/A
ρ=Resistivity
L=Length
A=Cross sectional area
The factor in the resistance which takes in to account the
nature of the material is the resistivity. Although it is temperature dependent,
it can be used at a given temperature to calculate the resistance of the wire of given geometry.
The inverse of resistivity is called conductivity. There
are contexts where the use of conductivity is more convenient
Electrical
Conductivity= σ =(1/ρ)
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