2: The First Law of Thermodynamics
- Page ID
- 32013
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- 2.1: The First Law
- The first law of thermodynamics is the conservation of energy, including the equivalence of work and energy, and about assigning an internal energy to the system. The first law of thermodynamics states that when an amount of heat dQ is supplied to the system and an amount of work dW is done by the system, changes are produced in the thermodynamic coordinates of the system such that dU=dQ−dW.
- 2.2: Adiabatic and Isothermal Processes
- Among the various types of thermodynamic processes possible, there are two very important ones. These are the adiabatic and isothermal processes. An adiabatic process is one in which there is no supply of heat to the body undergoing change of thermodynamic state. In other words, the body is in adiabatic isolation. An isothermal process is a thermodynamic change where the temperature of the body does not change.
- 2.3: Barometric Formula and the Speed of Sound
- Here we consider two simple examples of using the ideal gas law and the formula for adiabatic expansion. First, consider the barometric formula which gives the density (or pressure) of air at a height h above the surface of Earth. We assume complete equilibrium, mechanical, and thermal. The argument is illustrated in Fig. 2.1.1.