The First Law of Thermodynamics

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Physics Fluid Mechanics and Thermal Physics

	Work done on or by an ideal gas:
	When a gas undergoes a change from its initial state (P_i, V_i, T_i) to its final state (P_f, V_f, T_f) then the work done on or by a gas can be written as: The work done by a gas in the expansion from an initial state to a final state is the area under the curve connecting the states in a PV diagram. The work done by a system depends upon the initial and final states and on the path followed by the system between these states. Since, the heat and work depend upon the path neither quantity is solely determined by the end points of a thermodynamic process. For an ideal gas PV = nRT. Accordingly the expression for work done can be modified. The internal energy of an ideal gas: The change in internal energy of an ideal gas is given as follows: where C_p - C_v= nR Here C_p = Specific heat at constant pressure, C_v = Specific heat at constant volume, n = no of moles of an ideal gas, and R is the universal gas constant