Magnetic Permeability ... I can't find anyone talking about this !!!!!

[Charlie_V]

I'm not sure you can measure efficiency of a capacitor or coil based on time?  I'm not really sure how you can calculate that now that I think about it.  I guess it would be energy-in divided by energy-out.  So the amount of energy stored in a capacitor divided by the amount when it is discharged.  So for the coil, it will be the amount of energy stored in the magnetic field verses the amount of energy that comes out when it is shorted. 

I think time needs to be eliminated from the equation because once a capacitor is charged, the discharge could be nanoseconds or hours, but the same amount of energy will come out no matter what.  Same with a coil (accept the time constant on a coil is typically much shorter), but the same energy stored in the coil's magnetic field should be damn near the amount that comes out when the field collapses (minus some resistance in the coil).  Thats why with big wire gauges, the efficiency of the coil will increase.  500 feet of 10 gauge wire has about 0.5 ohms of resistance where as 28 gauge wire has 32.45 ohms.  The 10 gauge will be more efficient at storing energy but the coil will be larger.

Plus, another reason why we shouldn't involve time is that a rare earth permanent magnet can hold its field for an estimated 400 years, where as the best electret (look up electrets if you don't know what they are) can last MAYBE 20 years?  But the energy discharged in both at the end should equal the amount first stored in the beginning.  I think if you do the calculation these devices are close to 100% - pretty amazing if you ask me. 

[The Observer]

Hello Again,

I have been studying the Back EMF and Energy stored in an inductor physics.

Quickly, a good example what an coil acts like with current is to imagine a waterwheel.
  When water flows, it take a while to get up to speed.
  Conversely, when potential stops( the water moving), it takes awhile to slow down.
   
I can visualize this effect as the wave of single electron passing through the coil would get to the next coil, before the electron,
   as the electron needs to go around a circle where the wave does not.
This must be where the initial resistance comes in.

Then as current is stopped... it's wave needs to still pass through the coil...this is where the back emf comes in.

Now I looked the formula that has to do with energy stored in an Inductor.
Henries I believe.

Anyways, the effect is negligible, without a ferromagnetic core.

By that I mean...The energy stored (it's inductance) can be 5,000 times greater if a ferromagnetic material is used as it's core.

  So, this does bring us back to MAGNETIC PERMEABILITY.
  5,000 times greater is significant.

Wish, I could elaborate... but, I must get going.

       Creativity is more important than knowledge - (thanks Einstein)
                                                                                                 The Observer
                           

[fritz]

The inductivity increases with a core,
but you can squeeze more energy in a coil without
a core due to the fact that there is no saturation.

And anything curious which has somehow to do with a coil
and is to big that it fits in the head is Back EMF. of course.

sorry.

[MinEth3r]

Hi The Observer,

You might find this interesting:
   THE PARAMETRIC POWER CONVERSION
       A STEP TOWARDS OVERUNITY......
Created on April 16th, 1997 - JLN Labs - Last update : January 10th, 2003
    http://jnaudin.free.fr/html/paraintr.htm

Also, this better EM theory might interest you 
http://newelectromagnetism.com

Also, a recent effort regarding the classical - been discussed so many times before - cap anomaly:
http://ringcomps.co.uk/doc/

Best wishes!

[The Observer]

Hello Fritz,

You said,

The inductivity increases with a core,
but you can squeeze more energy in a coil without
a core due to the fact that there is no saturation.

I believe that is false.

Like I said, if you look at the formula, The MAGNETIC PERMEABILITY multiplies the energy stored or inductance.
Most Magnetic Permeabilities are about 1.
This doesn't do much ya know.... multiplying by 1.

  I will tell you what does though.
  Multiplying by 5,000 or more.
  The materials that do this are of ferromagnetic classification.

Saturation refers a point when the core can no longer add to the magnetic field of the coil.

That is, when a coil with a core becomes magnetized, the dipoles (and thus domains) start to line up with the field.
With a very small current and magnetic field produced by the coil, only  few of the domains start to line up.
  This is where amplification  begins.
   Then there is a point, as the magnetic field of the coil increases (due to increased current), that all dipoles in the core line up.
    This point is called saturation.

   The current can be increased, but the resultant increase in magnetic field after saturation is as if there were no core.

Anyone exploring this... please consider what a coil does with air or any other material as it's core, then compare with a ferromagnetic core.
  This is the reason this thread exists.

May the Sun Shine on your Back Door,
                                                        The Observer