# Individual states of a particular energy level

1. Feb 25, 2014

### abi.ayan

In thermodynamics what is meant by "the number of individual states that belongs to one energy level"?My current understanding is that different individual states of one energy means a system with different pressure,volume and temperature that belongs to a particular energy level?

plz can someone correct me if I am wrong?

2. Feb 26, 2014

### Simon Bridge

look and see what is meant by "energy level" and see.
the simplest thing to look at, though, is the 3D particles-in-a-box from statistical mechanics.

3. Feb 26, 2014

### abitslow

Like most things, few terms in Science have one single unambiguous meaning or definition. Words are tools, and just like any tool, they can be used in an infinite number of ways. Since you didn't give us the specific context :(
I'd have to speculate as to what the author meant. Not sure why you'd want us to do that? OK. Here goes:
In statistical thermodynamics, a microstate is the configuration of a COMPONENT of a (thermodynamic) system.
A common example would be the spin of a two particle system. A system ↑ ↓ would have the same energy as a system ↓ ↑ in most circumstances (where the arrows represent the spins of the two particles (atoms, electrons,..).
You can appreciate, using your imagination, what happens to the number of microstates in a macroscopic system. So, in all but the simplest cases, indeed the same energy level (of a population) will have numerous (configurational) states. Note that there is no requirement in my two spin example for the ↑ and ↓ states to have the same energy, indeed normally they won't. (In any sort of electrical field, if we're talking about charged particles...)
A more macroscopic example could be a bucket of balls...the exact position of each ball is a state, but there are an almost infinite number of similar configurations with the same energy. (picture balls of different colors, every time you mix them up, you've changed the system's configuration (microstate) but NOT necessarily its energy (with a bit of tamping, say).