2.2 The Second Law of Thermodynamics

Take-home message: You can't pass heat from the cooler to the hotter
Try it if you like but you far better notter
'Cos the cold in the cooler will get hotter as a ruler
'Cos the hotter body's heat will pass to the cooler

Courtesy of Flanders and Swann (full text reproduced, legally I hope, here.

There are two classic statements of the second law of thermodynamics

One due to Kelvin and Planck:

$\mbox{\colorbox{yellow}{\parbox{12 cm}{It is impossible to construct an engine ... ...f heat from a reservoir and the performance of an equivalent amount of work.}}}$

And another due to Clausius:

$\mbox{\colorbox{yellow}{\parbox{12 cm}{ It is impossible to construct an refrig... ...o other effect than the transfer of heat from a cooler body to a hotter one.}}}$

Note the careful wording: of course it is possible to think of processes which convert heat into work (expansion of a hot gas in a piston) or which pass heat from a cool to a hot body (real fridges) but other things change as well (the gas ends up cooler; you have an electricity bill to pay). The bit about ``operating in a cycle'' ensures that the engine is unchanged by the process.

The two statements may not appear to have anything to do with one another, but in fact each one implies the other. See here for details.

References

• (Mandl 2.1)
• Bowley and Sánchez 2.2
• Adkins 4.3
• Zemansky 6.6-8