Heat Engines - heat is imputed from a high temperature then some is converted to work and the rest in released as low temperature □ These topics are not quite tested on the AP exam anymore but used to show up on the exam several years ago and are taught in several college courses so we will quickly go over them. The second law of thermodynamics states that the total entropy (a measure of disorder) of a closed system will always increase over time, which is a consequence of this tendency toward higher disorder.This means that, over time, an isolated system will tend to move toward states with higher disorder, because those states are more likely to occur. ![]() States with higher disorder (or more randomness) typically have more ways that they can be reached, so they have a higher probability of occurring.In an isolated system, the probability of any given state occurring is proportional to the number of ways that state can be reached.This tendency can be described using the concept of probability, which is a measure of the likelihood of an event occurring.In thermodynamics, the tendency of an isolated system to move toward a state of higher disorder is known as the " arrow of time." Heat pumps and refrigerators are some of the most common examples. All real life engines perform irreversible processes. The entropy of the universe does increase due to irreversible processes. Irreversible - these processes can only be done in one direction. The gas is returned to its original state and no increase in entropy occurs. They consist of 2 adiabatic processes and 2 isothermal processes. A famous example of this is the carnot cycle. These processes do not increase the entropy of the universe: entropy stays constant. Reversible - these processes can be done forward or backwards. There are two types of thermodynamic processes we can think about based on entropy. Entropy at a point is the ratio between heat and temperature and is represented by the letter S. So the entropy or disorderness can either stay the same or increase.Ĭalculating entropy is not tested on the exam but we will learn briefly about it anyways in case you study it in college. The 2nd Law of Thermodynamics states that the entropy of the system and its surroundings will never decrease. The universe wants more disorder□ Entropy ![]() You can also define entropy as randomness or lack of predictability. Some people also define entropy as molecular freedom. ![]() That is the most surface level definition ever. This section might be one of the hardest to understand because it deals with intangible quantities, so just try your best□Įntropy is disorder. This section is heavy on theory and understanding of math rather than its application. which reduces the system performance.In this section, we finally get to the 2nd law of Thermodynamics. In the same article in which he introduced the name entropy, Clausius gives the expression for the entropy production for a cyclical process in a closed system, which he denotes by N, in equation (71) which reads In 1865 Rudolf Clausius expanded his previous work from 1854 on the concept of "unkompensierte Verwandlungen" (uncompensated transformations), which, in our modern nomenclature, would be called the entropy production. The importance of avoiding irreversible processes (hence reducing the entropy production) was recognized as early as 1824 by Carnot. Development of entropy in a thermodynamic systemĮntropy production (or generation) is the amount of entropy which is produced during heat process to evaluate the efficiency of the process.Įntropy is produced in irreversible processes.
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