COEFFICENT OF RESISTANCE
The coefficent of resistance is defined as the Increase in temperature per ⁰C divided by the resistance at 0 ⁰C. Where a is the coefficent of resistance

EXPERIMENTAL INVESTIGATIONS

In place of T the componet to be tested is placed in a temperature controled water bath. The resistance is calculated from V = I R, and the temperature incremented with the water baths controls, time is allowed for the bath and the component to reach equilibrium.

EXPLANATION
When the temperature of a metal is increased its resistance also increases this is because the increased vibration of the matel lattice makes it harder for the free electrons to flow easily through the material.
When a semiconductor is heated its resistance goes down as more electrons have the energy to become free from the lattice.