Thermal Conductivity — Definition, Formula, Dimension and Sample Values
( What is thermal conductivity? Thermal conductivity of a material designated as ‘k’) is the measure of how quickly heat energy is transferred or conducted from one end of the material to the other end. In this post we will work on the derivation of thermal conductivity expression first, then we will find its dimension as well.
A material with a high ‘k’ value will conduct heat faster than a material with a lower value of k.
If a steady temperature difference is to be maintained between the ends of say, a rod, then heat energy must be supplied at one end of the rod and the same heat must be taken out at the other end of the rod.
Here comes the importance of the ‘capability of heat transfer’ of the material. Materials of high k are used as heat sinks and materials of low k are used as thermal insulation.
Derivation of Thermal Conductivity Expression
Now we will derive the Thermal Conductivity expression.
=> k = [Q L] / [A (T1-T2) t ] …………………… (1)
Suppose heat energy Q is flowing through a rod of length L in time t.
To get the detailed step by step derivation to get the equation above :
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Definition of Thermal conductivity from its expression
From its expression in the previous paragraph, we can define Thermal conductivity.
When A = 1, t = 1, Temperature difference (T1-T2) =1 and L=1, then k = Q
Thermal Conductivity (k) is the quantity of heat transmitted due to a unit temperature difference between 2 ends of a conductor of unit length(or unit thickness), in ‘unit’ time under steady conditions in a direction normal to a surface of the unit area.
The dimension of Thermal Conductivity
Here we will find out the Dimension of k.
To find out the dimension of Thermal conductivity
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Some sample values of Thermal Conductivity k
Originally published at https://physicsteacher.in on October 16, 2017.