Heat flows from a material at a higher temperature to that at a lower temperature. Should't it flow from a material with a higher heat content to one with a lower heat content?
Just like how mass transfers from a higher concentration to a lower concentration where concentration is defined in terms of this mass itself, though, temperature has no physical definition as such!
Heat up a small piece of metal. Put it in a bathtub full of cold water. Choose the temperatures of the two such that the metal has a greater temperature, but the water has a greater heat content.
Afterwards, observe if the greater heat of the water has travelled to the metal, making it hotter, or if the greater temperature of the metal has resulted in its heat transferring to the water, making the metal cooler.
Then conclude if nature uses temperature or heat as the driving force.
Ohms law :
potential difference (Volts) = current x resistance
Thermodynamic law:
Temperature difference (kelvin) = heat (Watts) x thermal resistance
Temperature certainly does have a definition. In a gas it is a function of the mean velocity of the gas molecules.
Hope this helps
Paul
Heat is not a state variable. That is, it does not represent anything about the state of the system itself. Heat is "energy in transit" across a system boundary. The true driving force for many of these types of processes is chemical potential gradient. However, chemical potential is not easily measured nor was it really known or understood at the time that heat transfer was first being considered in the late 18th century. Kind of like mass diffusion. Concentration gradient is often used as the driving force (Fick's law) but it is the underlying chemical potential gradient that is responsible for the mass flux.
Hi Hitanshu,
Would just like to add one point to all the beautiful explanations above. The property specific heat capacity of a solid or fluid is also a function of temperature. Its variation with temperature is well established. So temperature determines the materials heat level too and therefore it makes sense for temperature difference to drive heat transfer.
Thank you all for your responses. A friend of mine just suggested something very intriguing about how we perceive temperature. We can think about temperature of a body as the distribution of heat within that body. So, if two different objects have the same temperature then the distribution of heat within them shall be similar and hence, on contact no resultant heat will flow even though one of the two objects may have a higher heat content.
Besides, potential = flux * resistance can be the perfect explanation!
One more question though: How do we define/interpret chemical potential?
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