On Wed, Apr 9, 2008 at 10:35 AM, Robin van Spaandonk < [EMAIL PROTECTED]> wrote:
> In reply to David Jonsson's message of Wed, 9 Apr 2008 08:47:15 +0200: > Hi, > [snip] > >> >Magnetic pressure is a well known concept. > >> >http://en.wikipedia.org/wiki/Magnetic_pressure > >> > > >> >It struck me then that other concepts must be applicable to magnetism > too > >> >like temperature. > >> > >> Temperature is really a measure of the average kinetic energy of > >> particles, so a > >> "magnetic temperature" may not have a lot of meaning. > >> > > > >Then magnetic pressure wouldn't either. > > Pressure is just energy density. While temperature is also a global > variable, > computing it wouldn't be so easy. E.g. > > For a gas one can use p*V/(nR) to get T (for a perfect gas). By analogy, > one > could substitute magnetic pressure for p, and the volume of the magnet for > V, > but what does one substitute for "n", the number of mole of magnetic atoms > in > the magnet? (not to mention what value to use for R). > This is why a precise definition of magnetic temperature is needed. The ideal gas law is empirical and nothing says that magnetic temperature would have a similar law. > >I have defined what I mean with > >magnetic temperature. > > Where? If kinetic temperature is kB*T=3/2 me*v^2 for a moving electron a similar reasoning could be applied. When the charged particle moves the magnetic energy Um (from the field energy B^2/2µ) becomes µ q^2 v^2 Um = ---------------- 12 pi r µ is permeability of surrounding medium q is the charge of the particle v is some averaged speed of particle r is the radius of the particle (if assumed to be spherical) Since µ will be dependent of the charged and ionized environment the value will be difficult to calculate. v would be some averaged speed of the particle. However with this definition magnetic temperature becomes Tm = Um/kB (or maybe 3Um/kB?) This would be applicable to monoatomic gases. For more complex molecules, lattices and metal plasmas additional modes of vibration and rotation would apply. This must be well investigated somewhere but probably with another name. David -- David Jonsson Sweden phone callto:+46703000370
