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?
