![]() ![]() Throughout this process, a portion of the energy is lost to entropy. A light bulb can convert this electrical energy to electromagnetic radiation (light), which, when absorbed by a surface, is converted back into heat. For example, a steam turbine can convert heat to kinetic energy to run a generator that converts kinetic energy to electrical energy. Heat can also be converted to and from other forms of energy. It can, however, be transferred from one place to another. As a form of energy, heat is conserved - it cannot be created or destroyed. Heat is energy transferred between substances or systems due to a temperature difference between them, according to Georgia State University. Thermodynamics, then, is concerned with several properties of matter foremost among these is heat. Often this is idealized as the mass of the system, the pressure of the system, and the volume of the system, or some other equivalent set of numbers." Heat But, if these systems meet the right criteria, which we call equilibrium, they can be described with a very small number of measurements or numbers. "The systems that we study in thermodynamics … consist of very large numbers of atoms or molecules interacting in complicated ways. Thermodynamics involves measuring this energy, which can be "exceedingly complicated," David McKee, a professor of physics at Missouri Southern State University told Live Science. This is one of the few situations where you can easily determine the work done by the gas in an irreversible expansion or compression.Īnd of course, for a massless piston, by Newton's third law, the work done by the gas on the piston is minus the work done by the piston (and atmosphere) on the gas.Thermal energy is the energy a substance or system has due to its temperature - in other words, the energy of moving or vibrating molecules - according to the University of Kentucky. From a force balance on the massless piston, the force per unit area of the gas on the piston face is equal to the external atmospheric pressure. In the situation you are describing, your only connection to the force per unit area exerted by the gas on the piston comes from the external specification. So the ideal gas law can't be used, except for the initial and final thermodynamic equilibrium states of the gas. So, in a rapid deformation, the gas behavior is not described by the ideal gas law. Secondly, there are viscous stresses present within the gas, such that the force at the piston face depends not only on the instantaneous volume of the gas, but also on the rate at which the gas volume is changing. First of all, the pressure of the gas within the cylinder is not uniform (as a result of gas inertia), so that the volume average of the local gas pressure within the cylinder differs from that at the piston face. But, in a very rapid (irreversible) expansion, the force per unit area acting on the piston face is different from that for a very slow deformation, for two reasons. The work done by the gas on its surroundings is equal to the force per unit area exerted by the gas on the inside piston face integrated over the volume change. So my question is, why are the two work calculated different? Is what I've done correct? One of my friend said that the way I'm calculating the work done by the gas on atmosphere is incorrect, if this is true, then what is the correct way?įirst let me say that you are correct, and your friend is incorrect. So, work done on atmosphere by the gas will be = - P1 * (change in volume of container).(or it should be an integral where pressure of gas changes from lower limit of P1 to an upper limit of P0). So, in this case, my system will be the atmosphere and surroundings should be cylinder contaning the gas. Now, I want to know the work done on the atmosphere. Now I know that work done on a system depends on external forces, so the work done on gas will be = P0 *(change in volume) Suddenly, the mass is removed and so the gas expands irreversibly to a final pressure of P0 which is the external atmospheric pressure. There is a block of mass m on top of the piston. Consider a cylindrical container contaning a gas with pressure P1 and volume V1 with a massless piston on top of the cylinder. ![]()
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