How is the rate of heat flow same in both conductors when the thermal conductivity constant is different for both conductors?I have seen this everywhere and have been confused regarding thisenter image description here

  • $\begingroup$ Showing that the rates of heat flow are equal at the interface is as simple as taking the time derivative of an energy balance. Note that when you combine identical heat flows with different thermal conductivities, you get different temperature gradients (i.e., different slopes of the temperature profiles) in materials 1 and 2. $\endgroup$ Feb 11, 2022 at 17:32

1 Answer 1


As there are no sources of sinks of heat within the conductors, so where else is the heat flowing through the first conductor going to go other than through the second conductor?

This is really not much different from having two resistors in series which have different resistance values (electrical conductivity vs thermal conductivity) with the current (flow of charge vs flow of heat) passing through them the same.

  • $\begingroup$ ok I understand that the heat flowing is same but the"rate of flow of heat"should be different right because both conductors have different thermal conductivity? $\endgroup$
    – AJknight
    Feb 11, 2022 at 9:36
  • 1
    $\begingroup$ You happy with current being the rate of flow of charge, so why are you unhappy with the rate of flow of heat (energy) being the same when considering thermal conduction? $\endgroup$
    – Farcher
    Feb 11, 2022 at 9:41

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