Electrical Engineering ⇒ Topic : Variation of Resistance with Temperature

Aditya
 
An increase in temperature increases the resistance of pure metals. If a conductor having a resistance of R_{0} 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, R_{0} 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 α_{1}is the temperature coefficient at temperature T_{1} and α_{2} is the temperature coefficient at temperature T_{2} and if we know al, T_{1} and T_{2}, we can calculate α_{2} from the following equation ................. (3) Similarly, resistivity or specific resistance of a metal also changes with temperature.The relationship between ρ_{0} 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  
 
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