Figure shows the P-V diagram of an ideal gas undergoing a change of state from A to B. Four different … I. (d) Work done is minimum…
Key concept: Internal energy (U): Internal energy of a system is the energy possessed by the system due to molecular motion and molecular configuration.
The energy due to molecular motion is called internal kinetic energy UK and that due to molecular configuration is called internal potential energy Up.
i.e., Total internal energy U= UK+ UP
(i) For an ideal gas, as there is no molecular attraction UP = 0
i.e., internal energy of an ideal gas is totally kinetic and is given by
U = UK = 3/2 RT
Change in internal energy does not depend on the path of the process. So it is called a point function, i.e. it depends only on the initial and final states (A and B) of the system, i.e. ∆U = Uf – Ui
Hence internal energy is same for all four paths I, II, III and IV.
The work done by an ideal gas is equal to the area bounded between P-V curve.
Work done from A to B, ∆WA→B = Area under the P-V curve which is maximum for the path I