Answer to Question #169515 in Molecular Physics | Thermodynamics for Khushi

Question

What is meant by internal energy of a system? State the first law of

thermodynamics in its differential form. Write it for isothermal, adiabatic and

isochoric changes, bita dp=alpa dT.

Answer 1

The internal energy of a body is understood as the sum of the kinetic energy of the chaotic movement of molecules and the potential energy of interaction of the molecules that make up this body. When calculating the internal energy, the kinetic energy of the movement of the whole body and the potential energy of the body in the external force field should not be taken into account. Also, the internal energy does not include intra-atomic energy.

$$dU=\delta Q-\delta A$$

For isothermal changes

$$\delta Q=\delta A$$

For adiabatic changes

$$dU=\delta A$$

For isochoric changes

$$\delta Q=dU$$