What is the difference between positive and negative temperature coefficient of resistance?

Answer 1

Negative temperature coefficient of resistance means that as the temperature of a piece of wire or a strip of semiconducting material increases, the electrical resistance of that material decreases.

Answer 2

Positive temperature coefficient is if temperature increased then resistance also increased but in negative temperature coefficient if temperature increasing then resistance must decreased.

Answer 3

The resistance of material is affected by the rise in temperature. Now both options are possible. That is either increase in resistance or fall in resistance as temperature increases. The first one is positive temperature coefficient and the latter is negative temperature coefficient.

Usually all metals and their alloys have positive temperature coefficient

But semiconductors and insulators have negative temperature coefficient. These are used as thermistors.