“We realized that the energy conversion associated with all the other quantities describing the gas, liquid, plasma, etc., when it is not in equilibrium are not included in the first law of thermodynamics,” Cassak told The Debrief. Cassak says that “when a system is out of equilibrium, the first law of thermodynamics continues to only describe energy conversion that changes the density and temperature.” The third point involves how a system, when out of equilibrium, continues to be described by the first law of thermodynamics. “So, one still has the density and temperature, but also many many more quantities,” Cassak says. Generally, there are almost an infinite number of different quantities that are needed to describe a substance under such conditions. “The second key point is that, for a gas, liquid, or plasma that is not in equilibrium, its properties can no longer be described by only the density and temperature,” he adds. “The first law of thermodynamics, then, describes energy conversion for a process that changes the density and/or temperature,” Cassak told The Debrief. Diagram detailing how between any two equilibrium states, changes in their internal energy is equal to the difference of heat transferred into the system and work done by it (Credit: NASA).Īccording to Cassak, there are three main points involved, the first being that for a simple, “ideal” gas, liquid, or plasma in equilibrium, its properties can be described by two main quantities: density, and temperature. However, Cassak and Barbhuiya say they devised a way to generalize the first law of thermodynamics, which allows it to be applied to systems that are not in equilibrium. Hence, explaining the energy conversion is more challenging. In certain settings (like with space plasmas), systems can be far from being near equilibrium, so the approximations do not work. “People have been working on extending the laws of thermodynamics for systems not in equilibrium for over 100 years,” he says. “Most of what people had figured out is how to extend the laws of thermodynamics for systems that are close to equilibrium. Even this is a huge step forward and has been useful in many fields of science.” “The part that has been challenging has been the theoretical work to figure out how to extend or improve upon the original laws of thermodynamics when systems aren’t in equilibrium,” Cassak told The Debrief. However, the conditions under which the laws of thermodynamics were developed at that time dictated that they would onlywork for systems in equilibrium, and Cassak says attempting to revise existing theories about thermodynamics hasn’t been a simple task. “The laws of thermodynamics were developed about 170 years ago,” Cassak told The Debrief, “and the technology of the time dictated the gases or fluids that people would have studied are in equilibrium at the densities and temperatures that they were using back then.”Ī good example of equilibrium would be how individual vessels filled with water at different temperatures within the same environment will eventually either cool or warm until they reach the same temperature. West Virginia University Professor Paul Cassak. Cassak is associate director of the Center for KINETIC Plasma Physics, where along with graduate research assistant Hasan Barbhuiya he studies the ways energy is converted in superheated plasmas in space. “The first law has been used to describe many things,” says Paul Cassak, a professor of Theoretical and Computational Plasma Physics at West Virginia University’s Department of Physics and Astronomy. More simply, the idea is commonly expressed as “energy can neither be created or destroyed.” The first law of thermodynamics, an expression of the law of conservation of energy albeit styled with relation to thermodynamic processes, conveys that the total energy within a system will remain constant, but that it can be converted from one form of energy into another. The discovery, involving how energy is converted in plasmas in space, was described in new research published in the journal Physical Review Letters, and could potentially require scientists to have to rethink how plasmas are heated both in the lab and in space. Physicists in West Virginia have announced a potential breakthrough that could help upend a longstanding constraint imposed by the first law of thermodynamics.
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