Magnetic materials have hysteresis in the B-H curve that causes work to be done when the magnetic field changes.
On Sun, Feb 28, 2016 at 11:34 AM, H Ucar <jjam...@gmail.com> wrote: > I observed dramatic heating of iron/steel rods of 2-4 mm diameter at 5 to > 10 mm distance to spinning Nd magnet of medium size above 8000 RPM (poles > nearly ortogonal to spin axis) where strong attraction is present. Motor > consumes extra 2-3 watts on this load. Heat can rise to 80 degrees C in > less than a minute, I guess, enough to melt hot glue. One atypical thing is > the hottest part is not the closest point to the spinning magnet, so far I > observed. Similar rods made of non ferromagnetic metals are not heated and > practically don't load the motor. Only large copper and Al blocks slow down > the motor but heating is not apparent. > > Any alternative explanation? > > >
