Thermal conductivity of a material may be defined as the
Thermal conductivity is the ability of a material to conduct heat, and it represents the quantity of thermal energy that flows per unit time through a unit area with a temperature gradient of 1° per unit distance.
The thermal conductivity of the material is given as
Q = kA(T1 − T2)t/x
T1 & T2 = Temperature of plate 1 & 2
x = Thickness of slab
A = Area of slab
k = Thermal conductivity of the body
t = time through which the heat flow has taken place
In the above equation if we substitute
A = 1m2
T1 − T2 = 1
t = 1
Q = K
It is thus obvious, that the thermal conductivity of a material is numerically equal to the quantity of heat (in joules) which flows in one second through a slab of the material of area 1 m2 and thickness 1 m when its faces differ in temperature by 1 K.
It may also be defined as the quantity of heat in joules that flows in one second through a one-meter cube of a material when opposite faces are maintained at a temperature difference of 1 K.