Temperature co-efficient of Resistance and its behavior with conductors

This article written about understanding about temperature co efficient of resistance and how it behaves with conductors. When we measure electric current in a electric load during different time it may show slightly current variation to lower side, event there is a constant voltage applied in it. The load may operates at different temperature according to its environmental conditions. So we may think that why it happen ?. Further we have studied that current flowing thorough a conductor is proportional to the resistance of it. So it is clears that when temperature increased in a conductor, it’s resistance also increased.

According to study with various conductors it is proved that ,

all conductor is a positive temperature co-efficient. Because , with increase of the temperature , resistance of the conductor is also increased.

Moreover we can classify the materials according to variation of resistance , while changes in temperature as follows

While Temperature increased in a materials (Let is consider as it drawn in unit length) , this resistance also increases. Such materials called as positive temperature co-efficient type

Eg: Copper, Aluminum

This materials resistance decreases with increases of temperatures. Such materials are called as negative temperature co-efficient type

Eg: Insulators like mica , rubber and semiconductors like silicon and Germanium

However the resistance varies in a material depends on following factors

1. Directly proportional to initial resistance
2. Directly proportional to the changes to temperature
3. It also depends upon the nature of the material of a conductor

Let the conductor has initial resistance R_o to the 0⁰C. Further that conductor heated to to t⁰C. So it will achieve a new resistance value R_t Ohm

So that resistance increased from R_o to R_t

Changes in Resistance ΔR = R_t – R₀

The changes of resistance is depends on following factors

R_t – R₀ α R₀ x t

Addition proportionality of material constant α₀

R_t – R₀ = α₀ R₀ x t

Where,

α₀ is known as constant, which represents temperature co-efficient of resistance at 0⁰C

   

So Temperature co-efficient of resistance can be defined as

The changes in resistance per ohm original resistance per degree centigrade change in temperature from 0⁰C

(or)

It is the ratio of the change in resistance per degree centigrade change in the temperature to the resistance at 0⁰C

To derive the unit of temperature co-efficient

   

Substituting respective units to the quantities

   

   

   

Hence the unit of temperature co-efficient of resistance is per degree centigrade

   

The above expression shows finding the resistance of conductor at any temperature, provided from initial resistance R0 at 0⁰C.