
Making Resistive Magnets (2009) - mindcrime
https://nationalmaglab.org/news-events/feature-stories/making-resistive-magnets
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cr0sh
So, a "resistive magnet" is basically the same thing as your school science
fair "bell wire wound on a nail" electromagnet, except it is made from very
precisely manufactured copper plates stacked with insulators and drilled to
accommodate flowing water. That's very interesting technology, plus the
nesting of the "coils" for multiple "layers" on the magnets.

It's kinda analogous to winding an electromagnet very carefully, but the
stacked design (along with the holes) allows for easy and effective liquid
cooling. It's a somewhat outside of the box thinking of magnet design.

I find it curious that I'm just learning about this now - I've never, ever
have seen this kind of magnet construction discussed anywhere (and it is
apparently a long-used technique)? I would expect such a design to be
discussed in numerous areas (or even just mentioned), but I've never seen
anything about it in popular press magazines or books, or anywhere else except
now?

I wonder why that is? Is it only because such magnets are for very specialized
use-cases, and fabricating one is outside the capability of most
organizations, let alone individuals? Or are the use-cases such that almost no
one else needs them (ultra-high current and high Tesla output) - and those
that do would be in the circles that know about this construction?

Again, I just find it strange; I mean, in my life, I've found books and other
sources that detail how to build STMs, CAT Scanners, and Radio Telescopes -
but nothing of the nature of a magnet like this (and overall, it's fairly
simple in concept and construction).

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m463
It would be nice to know sort of the "back of the napkin" scale for types of
electromagnets.

The magnets they talk about are 35 Tesla. I wonder what kinds of numbers you
get from a fridge magnet, a bell wire+nail, or a crt or.. how many teslas (T)
in a tesla (car)?

~~~
kwhitefoot
Most transformers and solenoids/electromagnets are less than 2 T (two Tesla)
because the saturation density isn't much higher than that for typical core
material. Much the same applies to electric motors.

See, for instance:

    
    
      https://en.wikipedia.org/wiki/Saturation_%28magnetic%29
    

and for some easily readable background on transformers showing simple
calculations for flux density:

    
    
      https://www.electronics-tutorials.ws/transformer/transformer-basics.html
    

The magnets described in the article don't have ferromagnetic cores so they do
not suffer from the same problem. On the other hand the technique is not
really applicable to power transmission or motive power.

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locmo
The bitter plate design process is one of the most beautiful things about
material engineering that exists!

