# Thermodynamics Definition and 1000 Threads

Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, biochemistry, chemical engineering and mechanical engineering, but also in other complex fields such as meteorology.
Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines, particularly through the work of French physicist Nicolas Léonard Sadi Carnot (1824) who believed that engine efficiency was the key that could help France win the Napoleonic Wars. Scots-Irish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated, "Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency."
The initial application of thermodynamics to mechanical heat engines was quickly extended to the study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged. Statistical thermodynamics, or statistical mechanics, concerns itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a purely mathematical approach in an axiomatic formulation, a description often referred to as geometrical thermodynamics.

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1. ### A Zeroth law of black hole thermodynamics

I was looking at the proof of zeroth law of thermodynamics from the original paper by Bardeen, Carter, Hawking, which can be found here. Now, we have the Killing vector which is the generator of the horizon, we call it ##l^\mu##, and auxiliary null vector field ##n^\mu##, which we define to be...
2. ### Thermodynamics: Possible process between a van der Waals gas and an ideal gas

Since the energy variation is zero: $$\Delta U = \Delta U_{1} + \Delta U_{2} = 0$$ The energy for a monatomic ideal gas is ## u = CRT##, and the energy for a Van der Waals gas is $$u = CRT - \frac{a}{v},$$ obtained through $$\frac{1}{T} = \frac{CR}{a + \frac{a}{v}}.$$ Summing the...
3. ### A Resistance Force on Gas in Magnetohydrodynamic Generator

I am attempting to derive equations of state for a flow loop that incorporates a magnetohydrodynamic (MHD) generator to extract energy from the working fluid, an ionized gas. I have been able to find the following equation to define the power output of the generator: (where K is load factor, σ...
4. ### Chemistry For irreversible process from state 1 to 2, why can the system not be isolated for reversible process from 1 to 2?

Then $$q_{irrev}=0\tag{1}$$ Take the system from state 2 back to state 1 using a reversible process B. My first question is: why can the system not be isolated for this reversible process to be possible? Assume we have a non-isolated system in process B. Process A and process B together...
5. ### B Is it possible to apply thermodynamics to magnetic/weak/nuclear fields

When I was taught about temperature in high school, I was told that substances that are hot have molecules that move fast, while substances that are cold have molecules that move slowly. I was also told that everything moves towards greater disorder or entropy. This is apparently because there...
6. ### Ratio of volumes in a vertical cylinder with a piston

First, I thought of the forces which are acting upon the piston. F1 + G = F2, where F1 = p1 * S and F2 = p2 * S p1 + mg/S = p2 I figured that before and after the gas' temperature rises, the piston has to be at equilibrium, so p2 - p1 = p2' - p1'. p1V1 = niu * R * T1 p2V2 = niu * R * T1 =>...
7. ### How to turn partition sum into an integral?

In, *An Introduction to Thermal Physics, page 235*, Schroder wants to evaluate the partition function $$Z_{tot}=\sum_0^\infty (2j+1)e^{-j(j+1)\epsilon/kT}$$ in the limit that $kT\gg\epsilon$, thus he writes $$Z_{tot}\approx\int_0^\infty (2j+1)e^{-j(j+1)\epsilon/kT}\,dj$$ But how is this...
8. ### Chemistry Is the differential of heat in a reversible process in an isolated system equal to zero?

If a process is irreversible, on the other hand, then $$\oint \frac{\delta q}{T}\leq 0=\oint dS\tag{1}$$ Apparently, from this equation we can conclude that $$dS \geq \frac{\delta q}{T}\tag{2}$$ How do we mathematically justify the step from (1) to (2)? Next, consider an isolated system...

46. ### I Where are the limits being taken in these thermodynamics equations?

Here is a passage from a book I am reading My question is about the limits. Are all the limits in the derivation above done for ##P_{TP}\to 0##? In particular, is it ##\lim\limits_{P_{TP}\to 0} (Pv)## that appears above? The author omits this information in all but the first limit and it...
47. ### I How to measure average thermal conductivity of a metallic material?

Heat conduction is the transport of energy between neighboring volume elements in a material as a result of the temperature difference between them. The "fundamental law of heat conduction", as it is called in the book I am reading, is a "generalization of the results of experiments on the...
48. ### Classical Finding the Right Physics Books for College for Students

Hi,I m studying for college and I need to receive some info from you guys. Which books should I use to study mechanics,thermodynamics,electricity and magnetism? I have no idea what books I should study because my own physics teacher has some pdfs in her USB and I can t borrow the USB because...
49. ### History - Evolution of ideas in the field of thermodynamics (statistics in mechanical and gas dynamics)

Hi, I have a question regarding the evolution of idea in the field of thermodynamics. Boltzmann is genereally credited with the notion of stasticis and it's relation to entropy. However, Boltzmann was inspired by the work of Maxwell (who himself followed the conceptual models of Bernoullli for...
50. ### I Application of the first law of thermodynamics

In Halliday's physics book, there is an example of the first law of thermodynamics that shows its application. The figure below explains this example: Here is a question, if the element alone is chosen as the system, doubts arise in the first law, because in this system, Q<0 (because heat is...