Question

What do you mean by temperature co-efficient of resistance being high and low?

Answer 1

The temperature coefficient is defined as ratio of increase in electrical resistance with increase in temperature which is denoted by Greek letter $\alpha$.

In case of metal the resistance is increased with increase in the temperature and hence they have positive value of $\alpha$.

With increase in temperature if the resistance of the metal decreases then $\alpha$ is said to have negative value.