Resistance

[olly_k]

Then there is the factor of negative coeficient of resistance where temperature increase causes a decrease in resistance such as used in thermistors.

But not in the case of silicon where an increase in temperature causes an increase in resistance, so called thermal runaway.

I think you meant a decrease in resistance, hence why semiconductors (triacs, transistors etc..) tend to destroy themselves if allowed to get too hot!

 

[Adam_151]

Interesting demo described to me by one of my phyics teachers (but obviously H&S wouldn't allow it to be demo-ed in the classroom):

A glass rod is clamped in place, and connected to the mains supply with a croc clip on each end, a polycarbonate screen is placed in front, and the centre of the rod is heated with a flame, then the flame is taken away. The heat has decreased the resistance enough for a significant current to flow, which heats it up more, further reduceing the resistance and allowing more current to flow and the termperature to increase, the process continues until the rod melts right through (or a fuse blows)