PPT Slide
Most probable configuration:
- Let two systems (S1 and S2 be in contact) so that energy can be transferred from one to the other (thermal contact)
- S=S1+S2 another larger system. We have for internal energy: U=U1+U2.
- let us consider S isolated (U, V, N….constant)
- what determines whether there will be a net flow of energy from one system to another? --> concept of temperature
- the most probable division of the total energy is that for which the combined system has the maximum number of accessible states!
- let us consider the case of thermal contact of two systems. The numbers of particles in system 1 is N1 and in system 2 is N2, the values of the energies in system 1 is U1 and in system 2 U2. The total energy U=U1+U2 is fixed.
(g(N,U) is the multiplicity function of system S, g1,2 for system 1,2 respectively.)
a configuration : set of all states with specified values of U1 and U2..
most probable configuration: the configuration for which g1g2 is maximum
- if N>ɭ fluctuations about the most probable configurations are small
Schematic representation of the dependence of the configuration multiplicity on the division of the total energy between the systems S1 and S2
- values of the average physical properties of a large system in thermal contact with another large system are accurately described by the most probable configuration! --> such average values are called thermal equilibrium values
average of a physical quantity over all accessible states --> average over the most probable configuration