How Does Adding Impurities Affect the Conductivity of a Conductor?
Let’s Consider the effect of adding impurities on the conductivity of a conductor.

Again, Let's look at the factors that go into conductivity and consider how each of these are affected:
sigma = n q m      

Conclusion:
The electrical conductivity of a conductor will decrease with an increase in impurities!

Again the relationship is not linear, however, if we consider the resistivity, which is the reciprocal of conductivity, we do get a linear relationship:
rho = rho0[1 + beta x]
where

Here is a plot showing the variation of electrical resistivity with composition (impurity additions) for various copper alloys. The data is fixed at room temperature (20oC).
variation of electrical resistivity with composition (impurity additions) for various copper alloys. The data is fixed at room temperature (20oC)
 


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