XPost: sci.electronics.design   
   From: bill.sloman@ieee.org   
      
   On 20/02/2026 12:36 am, Jeroen Belleman wrote:   
   > On 2/19/26 13:39, Bill Sloman wrote:   
   >> On 19/02/2026 9:56 pm, J. J. Lodder wrote:   
   >>> Bill Sloman  wrote:   
   >>>   
   >>>> On 19/02/2026 7:49 am, Ross Finlayson wrote:   
   >>>>> On 02/18/2026 12:43 PM, Python wrote:   
   >>>>>> Le 18/02/2026 à 20:13, Ross Finlayson a écrit :   
   >>>>>> ..   
   >>>>>>> and, you know, magnetic monopoles, is widely employed   
   >>>>>>> in medical imaging and the like.   
   >>>>>>   
   >>>>>> No.   
   >>>>>   
   >>>>> Resonance imaging (NMR) is a thoroughly different mechanism   
   >>>>> than Roentgen rays.   
   >>>>   
   >>>> But as the name implies, it's nuclei of the atoms involved that exhibit   
   >>>> the resonance. It's a remarkably low energy effect, and you need   
   >>>> remarkably high magnetic fields to get it to give you a detectable   
   >>>> signal.   
   >>>   
   >>> Nevertheless, it is easily demonstrated in the kitchen   
   >>> with some simple electronics.   
   >>   
   >> Sort of.   
   >>   
   >> https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance   
   >>   
   >> There are lots of different ways to exploit nuclear magnetic resonance.   
   >> The earth's magnetic field is high enough to let you devise   
   >> experiments that can demonstrate the effect on a kitchen table.   
   >> Medical imaging works a lot better with high fields. In 1979 I got to   
   >> ask the EMI Central Research NMR imaging development team why they   
   >> weren't using super-conducting magnets, and got told that you couldn't   
   >> modulate the field.   
   >>   
   >> The fact that you couldn't modulate the total number of flux lines   
   >> threading a super-conducting coil didn't mean what they thought it did   
   >> at that time.   
   >   
   > "Number of flux lines"?   
      
   I was responding to a half-wit. If you integrate the total magnetic   
   field strength across the bore of super-conducting coil, it is   
   determined by the current circulating around that coil, but you can make   
   arrangements that permit the local field to vary from place to place   
   within that area. Faraday did like to talk about flux lines - it does   
   make the idea easier to get across. I didn't try back in 1979 - we were   
   being told about what was going on by people who had a high opinion of   
   their own expertise.   
      
   --   
   Bill Sloman, Sydney   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)