Internal energy

Total energy contained in the system is called its internal energy. It is denoted by E or U. Internal energy of a system is continued by different components like kinetic energy, potential energy, rotational energy,vibrational energy, transitional energy, band energy, molecular energy etc. Among them value of components cannot be determined accurately. So the exact value of the system cannot be determined accurately. In thermodynamic calculation of the exact value of internal energy of a system has no importance. We need the change in internal energy of a system for different thermodynamic calculation and we can determined the change in internal energy of a system experimentally.
Suppose a thermodynamic system is changed from state1 to stat2.Let E1 and E2 be the internal energy of initial and final states respectively.Then change in internal energy is total energy is given by
Total energy=E2-E1
The change in internal energy of a system is state function because it depends only upon the initial and final states of system, it does not depends upon the path in which that a change is carried.

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