inductor/transformer concepts

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Laurence Davis by way of Terry Fritz <twftesla-at-qwest-dot-net>" <meknar-at-hotmail-dot-com>

this may be considered off topic, but perhaps learning some theory would 
help some of us better understand the coil as well...
(ok I might be rationalizing)

I'm interested in building a transformer for my coil.  I've realized I don't 
have an EE degree and will need to learn several key concepts before I 
design one.  heres a few questions I have regarding magnetic flux.  I'm just 
trying to understand key relationships and concepts.

primary turns intended to induce flux in a core:  too many turns or too 
small core can cause core saturation.  too little turns or too large of a 
core could not create enough flux to induce current in sec.  as a wire can 
be compared to a pipe and current is volume that flows within that pipe, so 
as to magenetic flux that flows within the core.(this seems incomplete)

core materials: soft iron is used for lower frequencies and ferrite cores 
are used for higher frequencies. why? I figure that it is the material's 
capability to retain... ok, let me rephrase that. I look at it like this:  
the flux moves through the material. but instead of looking at it like a 
wave; i'm looking at like a 'particle' or charge. so the core material 
'molecule' holds a specific spin or flux for a specific amount of time. the 
materials characteristics state that it can hold this flux for x time.  this 
determines how the flux propagates through the material. for soft iron, more 
flux is needed to raise material's flux, but it retains it for a longer 
time.  but ferrites respond to a smaller amount of flux, but retain it for a 
shorter period.
soft iron used in a ferrite application would then not receive enough flux 
to be 'efficient'(too little flux), and a ferrite used in a soft iron 
application would then become saturated.

how does an air core relate to the above scheme?  or how does the field of a 
coil change when it does not have a core (as in it has an air core)?

Also is it true that eddy currents resist the pri coils flux? (and resist 
the secondaries induction of current) why use laminations? why does this 
help?  now there are many fields in the core.

larry d.