Thermal Conductivity

Thermal conductivity is a qualitative measure of how readily a solid conducts heat through it -- a good conductor of heat has a HIGH thermal conductivity, a bad conductor (insulator) has a LOW one. If one end of a rod is suddenly heated (Fig. 7.12(a)), every cross-section along the rod starts warming up over time -- this is called the variable-temperature state. Eventually, each cross-section settles at its OWN constant temperature that no longer changes with time (though different cross-sections still have different temperatures from each other) -- this is the STEADY STATE. In the steady state, temperature decreases uniformly with distance from the hot end towards the cold end, along the direction of heat flow; this fall of temperature per unit distance is called the temperature gradient: …