The First Law of Thermodynamics

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Physics Fluid Mechanics and Thermal Physics

Heat Capacities of an ideal gas:

The heat capacities of any gas are of two types. One is specific heat capacity at constant pressure and the other one is specific heat at constant volume. The specific heat at constant pressure is given as:

Similarly, the specific heat at constant volume is given as:

These two heat capacities are related to each other as:

Applications of First Law of Thermodynamics:

Before the application of first law of thermodynamics we must know the following things:

(a)	The process that takes place at constant heat so that it is isolated from the surroundings, it is called adiabatic process.
(b)	The initial and final internal energies of a gas are equal in an adiabatic free expansion.
(c)	The thermodynamic process that takes place at constant pressure is called isobaric process.
(d)	The thermodynamic process that takes place at constant volume is called isovolumetric Process.
(e)	If energy is added by heat to a system kept at constant volume, then all of the transferred energy remains in the system as an increase of the internal energy of the system.
(f)	A process that occurs at constant temperature is called isothermal process.