Thermodynamics

= Thermodynamics =

__Thermodynamics__ is the study of processes that involve energy being transferred as __heat__, which is defined as a transfer of energy due to a difference in temperature, or __work__, which is a transfer of energy that is not due to a difference in temperature. Usually in discussing thermodynamics a system and its surroundings have to be defined. A system is simply an object (or multiple objects) that are being considered. The surroundings are simply everything else.

The First Law of Thermodynamics is most easily defined in an equation: (Change in U) = Q + W, where U is internal energy, Q is heat and W is work

Some thermodynamic processes are: Also in thermodynamics a heat reservoir, a body so large that when heat is exchanged with the system, the temperature does not change significantly, is usually implemented in order to create an isothermal process. This is a Pressure vs. Volume Diagram. Get used to it, has it will haunt you for as long as you deal with Thermodynamics. It looks more complicated than it seems, but once you understand all the terms and processes, this thing will be a breeze to read. Like for instance, one can find the work done during a particular process, say from 3 to 2. The work is simply the area underneath the line connecting 3 to 2. See, wasn't that easy?
 * Isobaric
 * Constant Pressure; When Pressure is constant, W = P(Change in V). (P is Pressure, V is volume)
 * Isothermal
 * Constant Temperature; In an ideal gas, Change in U = 0 and Q = -W
 * Isovolumetric/Isochoric
 * Constant Volume; W = 0; Q = Change in U
 * Adiabatic
 * No heat is allowed in or out of the system; Q = 0; Change in U = W

Thermodynamics are applied to Heat Engines, Refrigerators, Air conditioners, heat pumps and the like. Heat and work, whether going in or out, are used to measure things such as efficiency (e = W/Qh) and Coefficient of Performance ( COP = Ql/W (refrigerators, Air conditioners); COP = Qh/W for Heat Pumps.)

 A Diagram for a heat pump

<span style="font-family: 'Arial Black',Gadget,sans-serif;">One specific heat engine that you will come across is the Carnot Engine. This engine is purely hypothetical, and is used mainly for grasping the thermodynamic processes. This ideal engine has four processes: two of which are isothermal expansion and compression and the other two are adiabatic expansion and compression. The PV Diagram above actually represent the Carnot Cycle. Physicists even have an equation to find the ideal, or Carnot efficiency: e(ideal) = Th - Tl/Th <span style="font-family: 'Arial Black',Gadget,sans-serif;">= 1 - Tl/Th

<span style="font-family: 'Arial Black',Gadget,sans-serif;">The Second Law of Thermodynamics is fairly simple as well. The Law can be written in terms of variables, but before we get to that, first we have to figure out what Second Law is. Second Law is concerned with the idea of entropy, or disorder, saying that natural processes tend to move toward a state of greater disorder. The equation is: Change in S = Q/T (S = entropy; Q = Heat; T = Temperature (Kelvin)). <span style="font-family: 'Arial Black',Gadget,sans-serif;">The other ways the Second Law can be stated are like so:
 * <span style="font-family: 'Arial Black',Gadget,sans-serif;">Heat flows spontaneously from a hot object to a cold one, but no the reverse.
 * <span style="font-family: 'Arial Black',Gadget,sans-serif;">There can be no 100% efficient heat engine, one that can change a given amount of heat completely into work.

<span style="font-family: 'Arial Black',Gadget,sans-serif;">Here's a link to another website that goes more in-depth: Thermodynamics