Moving Iron question

As I understand it, the motion of a magnet relative to a fixed coil will induce a varying current in that coil. Similarly the motion of a coil relative to a fixed magnet will induce a varying current in the coil. How does a Moving Iron Cart like the Grado or Soundsmith induce a current when the moving element is neither a coil nor a magnet. Any help here?

Thanks in advance,

Hope that this helps Grado Cartridge Structure. Click on the top tab marked "Cartidges"

Thanks for the link, but the Grado explanation is that the moving iron element creates an increase in one flux gap and a decrease in another as it moves back and forth on the cantilever. I don't quite understand what that means or how it induces a current. If there were already a constant current, I think I understand how it could impede that as it moves, but I don't understand how it could induce current.

'Induction' means that a field from a magnet is used to strengthen the smaller field of a magnetic material attached to the cantilever by means of proximity. The smaller material can be iron oxide.

This increases the field strength and keeps the moving mass low.
Thanks Story, I didn't realize that iron meant iron oxide = magnet.


You are mistaking a magnet for magnetic field. Magnets have permanent magnetic fields around them but you can modify the flux lines (shape of magnetic field) by what materials you place close to the the magnet and coil sensor do not have to move in order to induce current in a coil ...provided you change the field by moving something close to it.

An iron core is the same thing you have in a transformer - it concentrates magnetic flux lines and increases the magnetic field locally.
Got it.