Editing 2063: Carnot Cycle

This comic shows a {{w|Pressure–volume diagram}} which is used in this case for a {{w|Carnot cycle}}, a theoretical thermodynamic cycle covered in most thermodynamics classes which looks a lot like the figure drawn. The most common example of a (suboptimal) Carnot cycle is the {{w|Heat_pump_and_refrigeration_cycle|vapor compression cycle}} used in {{w|Refrigerator|refrigerators}}. However in this case, [[Randall]] has replaced the labels of the 4 stages of the real Carnot cycle with new ones.

Pressure–volume diagrams were first developed to understand the efficiency of steam engines and plot the change of pressure ''p'' with respect to volume ''V'' for a specific process. The process forms a cycle and the amount of energy involved can be estimated by the area under the curve on the chart. The Carnot cycle describes the ideal efficiency that such an engine can achieve during the conversion of heat into work, or vice versa like in a refrigeration system. The real steps are called (explained in short):

#'''Isothermal expansion''' (An external heat source causes an increase of volume and an antiproportional lowering of pressure, driving the motor. It's more efficient if this step is performed slowly.)

#'''Isentropic expansion''' (The volume of the gas increases further while the pressure decreases dramatically, as the external heat source is now absent, transforming heat directly into work, lowering the Temperature. This step is more efficient, if it goes quicker.)

#'''Isothermal compression''' (External cooling and a small amount of work from another part of the machine decreases the volume of the gas and leads to the last step:)

#'''Isentropic compression''' (Now the gas is sharply compressed, using part of the work from step two to return the gas to the beginning of step one, raising the Temperature back up.)

{{w|Isotonic}} is a descriptor commonly associated with sports drinks (and not thermodynamics), which contain similar concentrations of salt and sugar as in the human body. {{w|Dark energy}} is hypothesized to be a cause for the accelerating expansion of the universe, which obviously isn't relevant to thermodynamics (yet). The [https://hypertextbook.com/facts/2002/AliciaNoelleJones.shtml density of milk] depends on milkfat and solids-non-fat, which includes lactose. Fortified milk has increased solids-non-fat but the same percentage of milkfat, resulting in increased calories and an increased density. So the fortification of milk results in increased calories, possibly referred to as dark energy, and a contraction, as less space is needed for 1 kg of milk. However, this explanation does not match the expansion suggested in the comic.

 

Later Randall again combined dark energy (and also dark matter) with milkfat in [[2216: Percent Milkfat]].

{{w|Isopropyl alcohol}} is commonly used for cleaning. Inflation and contraction could refer to changes in gas volume, but the reference to {{w|interest rate}}s puts them in the context of {{w|macroeconomics}}. Raising ("tightening") interest rates tends to reduce {{w|inflation}} and/or "contract" the economy. High interest rates are a feature of the third stage (recession) of the {{w|Juglar cycle}}. In economics (and other sciences) to better understand model parameter relations, some parameter may be held constant in theory. This could refer to the {{w|Fisher equation}}. Holding one parameter constant is also done in the Carnot cycle (for a physical parameter): not only in theory but also in practice! (In free market economies the inflation cannot be directly held constant).

 

{{w|Galadriel}} is a character in ''{{w|The Lord of the Rings}}''. She is one of the leading {{w|Elf (Middle-earth)|elves}}, a race that in the time of the book is said to be dwindling (in number and importance) in {{w|Middle Earth}} and migrating westward to {{w|Valinor}}. Galadriel is one of the last elves to leave, after successfully resisting temptation to take the One Ring and become an all-powerful queen who dominates Middle-earth, instead saying "I will diminish, and go into the West, and remain Galadriel." The title may be a reference to {{w|Edward Gibbon}}'s 18th century masterpiece ''{{w|The History of the Decline and Fall of the Roman Empire}}'', or to the novel ''{{w|Decline and Fall}}'' by {{w|Evelyn Waugh}} (which is itself a reference to Gibbon's book). This stage is present in the cycle because in the real cycle, at this stage, volume of the gas decreases without exchange of heat. It is the last stage after which the gas has its original value of variables, thus completing the cycle.