Internal Energy of a System


The internal energy of the system is the sum of the kinetic and potential energies of the system.

The kinetic energy of the system is the energy of molecules which are moving inside the system.  The kinetic energy of the system increases with the increase in temperature.

The potential energy of the molecules in the system is the result of the interatomic forces acting on the molecules.  For example, electrostatic forces can cause the attraction and repulsion of the atoms.

The sum of the kinetic and potential energies of the sytem is called the internal energy.

Temperature and Internal Energy

The Internal Energy is directly proportion al to the temperature of the system.  This is because, the a rise in temperature increases the kinetic energy of the system.

Consequently, this causes a change in Internal Energy as well.

At absolute zero (0 K or -270 deg. C), the internal energy of a system is zero.

Change in Internal Energy

The change in internal  energy depends on the change in temperature of the system.

dU = mCv (T1 - T2)

where
m is the mass of gas in kg
Cv is the specific heat at constant volume in kJ/kg.k

Posted by: Electrotechnik