What is internal energy?

Arslan Avanesov
Arslan Avanesov
January 16, 2013
What is internal energy?

The size of the internal energy of the body is usually denoted by the Latin letters E and U. The concept of the internal energy of the body implies the sum of two types of energy of molecules that make up the body - the energy of molecular interaction and the energy of thermal motion of the molecule. Internal energy is a unique function that determines the state of the system. That is, in cases where the system assumes a given state, the internal energy of this system takes the value corresponding to the given state. From this it is clear that the indicator of changes in the internal energy of the body is equal to the difference between the values ​​of the final and initial state of the system. It does not depend on the transition path.

There are two ways to change the internal energy of the body:

  1. Job
    • friction
    • deformation
  2. Heat transfer
    • convection
    • thermal conductivity
    • radiation

In the case when the action is performed on the body, it increases its internal energy. In the case when the action is carried out by the body itself, then it reduces its internal energy.

There is also the concept of internal energy of gas.What is the internal energy of an ideal gas? This value is determined by the sum of the kinetic energies of the constituent particles of the system. In this case, the potential energy of molecules is usually neglected.