Electrical Engineering ⇒ Topic : Variation of Resistance with Temperature

 An increase in temperature increases the resistance of pure metals. If a conductor having a resistance of R₀ at 0°C is heated to a temperature 1°C, its resistance increases. Let the new resistance be R_T. The net increase in resistance is (R_T -R_O). This can be written as:

                                                                                   ...............     (1)

where,  α (Greek symbol, Alpha) is a constant and is called the temperature coefficient of resistance of the material of the conductor. From Eq. (1) we find that

                                                                                         .............      (2)

where R_T is the final resistance, R₀ is the initial resistance, T is the difference between the final and the initial temperatures and a is the temperature coefficient of resistance of the material. The temperature coefficient of some metals which are widely used as conductor is given in Table .

                              TABLE  Temperature coefficient of resistance of different metals

So far, we have assumed that a does not change with temperature, but in most metals it does change with temperature. If  α₁is the temperature coefficient at temperature T₁ and α₂ is the temperature coefficient at temperature T₂ and if we know al, T₁ and T₂, we can calculate α₂ from the following equation

                                                                                  .................   (3)

Similarly, resistivity or specific resistance of a metal also changes with temperature.The relationship between ρ₀ and ρ_i, can be written as

                                                                                              ...................   (4)

Equations (2), (3) and (4) describe the variation of resistance, temperature coefficient and resistivity of a material with variation in its temperature