Resistance vs. Temperature

does an increase in temperature increase the resistance in the following?most materials?carbon?
- josh (age 16)
australia

In metals, increasing temperature typically increase resistance because it causes the electrons to scatter off more thermal phonons, decreasing the time before they lose their momentum. In semiconductors increasing temperature typically decreases resistance because it allows more electron-hole pairs to form, and the current is carried by electrons and holes.

For carbon, it depends on the form. Probably you're thinking of graphite, a semimetal, for which there are a few charge carriers even at zero temperature. The net effect is still more semiconducting, in that resistance goes down as temperature goes up. Another form, diamond, is a pure semiconductor.

Mike W.

(published on 08/11/2016)