We will discuss here about effect of temperature on resistance
Resistance of pure metals increases with increase in temperature. For metallic conductor this variation of resistance with temperature is linear
The variation of resistance with change in temperature is shown here as a line
Let us measure the resistance of a metallic conductor and also let us record the temperature
at the time of measurement of resistance. Now let us heat up the conductor for some time
and measure the resistance and temperature again. Here R0 and T0 are the measured resistance and
temperature of the conductor at first time and R suffix T and T suffix T are the resistance
and temperature of the second measurement. Now due to change of temperature how much
resistance will be changed depends on the actual resistance of the conductor at initial temperature
In a simple manner if resistance of the conductor is more the change will be more and if resistance
of the conductor is small the change will be small. Hence the change in resistance due to
change in temperature is found to be directly proportional to the initial resistance that is
RT minus R0 is proportional to R0. It is also needless to say that change of resistance depends
on how much the temperature of the conductor has been changed. That means if variation of
temperature is more the change in resistance is more and vice versa. That means RT minus R0
is also directly proportional to the temperature rise T suffix T minus T suffix 0. Let's say it is T
This change also depends upon the nature of the material. That means for same temperature
variation different metallic conductors of same resistance show different changes in their
resistance. Thus we can express the change in resistance as RT minus R0 is directly proportional
to R0 into T or RT minus R0 equals to alpha 0 R0 into T where alpha 0 is also called the temperature
coefficient of resistance at 0 degree centigrade or RT equals to R0 into 1 plus alpha 0 T
This expression can be applied for both increase and decrease in temperature. From the graph of
the figure it is seen that resistance of the material continues to decrease with the decrease
in temperature below 0 degree centigrade. If we go on decreasing the temperature to a very low value
the material attains a state of zero resistance. The material at that state becomes superconducting
that is conducting with no resistance at all. This condition is not practically possible. That means
no conductor can get zero resistance property. Hence this graph will not touch the horizontal
axis. Instead it will be parallel to this horizontal axis. This diversion of graph
indicates that the resistance of any conductor will become constant after a certain minimum
temperature. After this minimum temperature the resistance will decrease no more. Hope you got a
clear idea. Thank you