Re: [Phys-L] let's define energy

[John Denker <jsd@av8n.com>]

On 09/29/2015 03:25 PM, Diego Saravia wrote:

> R has energy units inside it.

I disagree.  R has dimensions of energy per unit energy
per mole.  The energy factors drop out.
 
> and physical entropy the same

Yes, molar entropy has the same dimensions as R, but 
no, it does not have dimensions of energy.
 
> shanon entropy has not units it is adimentional

Units are not the same as dimensions.  Angles are
dimensionless but they still have units, such as
milliradians, degrees, percent, cycles, or whatever.

So it is with entropy.  It is dimensionless, but it
still has units.  For small amounts of entropy, a
convenient unit is "bits".  For large amounts of 
entropy, a convenient unit is "joules per kelvin".

	1 J/K = 1.04×10^23 bits

Macroscopic entropy differs from microscopic entropy
only in magnitude, not in kind.  If they were different
in kind, it would seriously break the 2nd law of
thermodynamics.

> do you see temperature as a sort of energy? 

Yes, absolutely.  For example, in the expression

       dE = T dS             (under some conditions)

there is energy on the LHS.  The energy on the RHS
comes entirely from the T, not from the dS.