It is normal when the temperature of a material increases, the resistance increases in the most of conductors, insulators decrease in resistance, whilst the resistance of some special alloys remains almost constant.
The temperature coefficient of resistance of a material is the increase in the resistance of a 1OHM resistor of that material when it is subjected to a rise of temperature of 1◦C. Greek alpha is the symbol which is used for the temperature coefficient of resistance is “α”.
Thus, if some copper wire of resistance 1OHM is heated through 1◦C and its resistance is then measured as 1.0043OHM then α=0.0043Ω/Ω◦C for copper. The units are normally expressed only as ‘per ◦C’, i.e. α=0.0043/◦Cfor copper. If the 1Ω resistor of copper is heated through 100◦C then the resistance was at 100◦C would be 1+100x0.0043=1.43Ω_.
