How does temperature effects electrical resistance?
Answer:
Heat decreases the electricity carrying capacity of a conductor (i.e. resistance increases). Cold reduces the resistance in conductors. The size of the effect depends on the particular conductor.
Super-conductivity is a phenomenon observed at extremely cold temperatures (near absolute zero or -273ยบ C). With super-conductivity, ALL electrical resistance is lost, and the energy at the end of the line is the same as the energy put into the line (i.e. no transmission losses).
There are some exotic materials with "near-room" temperature super-conductivity, but even "near-room" temperature to scientists is a lot colder than any room you'd ever want to be in.
for most of the solid/liquid substances, resistance decreases with decreasing temperature
higher temp. = more resistance
lower temp. = less resistance
R = rho x L / A
R, Resistance
rho, Constant
L, Length of wire
A, cross sectional area
An increase in temperature generally increases electrical resistance.
Why? In the semi-classical model, with free electrons bopping about the conductor, when a voltage is applied, the electrons pick up momentum from the electric field until they scatter off the metal lattice. Then they start to pick up momentum again. But the more often they scatter, the slower their average velocity.
And the higher the temperature, the more often the lattice vibrations cause the electrons to scatter.
So the higher the temperature, the more frequent the scattering, the slower the average velocity, the lower the total current. Less current for same voltage => higher resistance.
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