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What does a negative temperature coefficient of resistance mean?

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xllx
#1
Feb12-09, 12:23 PM
P: 33
If a material has a negative temperature coefficient or resistance, what does this mean?

Does it mean that as temperature increases, the resistance will increase instead of decrease.
Or something totally different?

Any help at all would be greatly appreciated! Many Thanks!
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mgb_phys
#2
Feb12-09, 12:48 PM
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Other way round.
The conductivity increases with temperature, ie resistance decreases.

In general, electrical resistivity of metals increases with temperature (+ve), resistivity of semiconductors decreases with increasing temperature (-ve).
Mapes
#3
Feb12-09, 12:55 PM
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Quote Quote by xllx View Post
If a material has a negative temperature coefficient or resistance, what does this mean?

Does it mean that as temperature increases, the resistance will increase instead of decrease.
Or something totally different?
It means that the resistivity will decrease (or the conductivity will increase) with an increase in temperature. This is a common feature of semiconductors, because the number of charge carriers increases strongly with temperature. In metals, conversely, the number of charge carriers isn't strongly dependent with temperature. Instead, the dominating effect is increased carrier scattering with temperature. This results in a positive temperature coefficient of resistance: increased resistance due to a temperature increase.


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