Conventional Magnets: Other Characteristics

A very strong holding force requires an equally strong release force.  This basic conundrum of conventional magnets limits their usefulness for many applications.  Often, we want their attraction forces to be strong but not too strong.  For example, we want to achieve a strong seal for a refrigerator door but we must limit the strength of the magnets used to provide that seal so that we are able to open the refrigerator door.  Stronger magnets could provide a far superior seal but …

Translational surface alignment of two coupled magnets is unpredictable.  Magnets may only partially align if the force between their surfaces plus friction is at least equal to the torque tending to orient their magnetic moments.  Generally, two magnets associated with two objects cannot be depended upon to provide precision translational surface alignment since the magnets can couple and remain misaligned when the two objects are brought together.     

Rotationalsurface alignment of two coupled magnets is unpredictable. Magnets can couple with any of multiple rotational surface alignments relative to each other (depending on their shape) as long as surfaces having opposite polarities are brought together.  Round magnets will couple at any relative rotation to each other.  Very strong square magnets can be coupled at any of four different rotations.  Weak magnets can be coupled at any relative rotation regardless of their shape.  Generally, two conventional magnets cannot be depended upon to achieve precision rotational surface alignment.

Strong magnets can be very dangerous and can cause problems.  Strong magnetic forces can propel one magnet into another, propel nearby metal objects to the magnet or vice versa, and strong magnetic fields can have adverse effects on pacemakers, credit cards, cell phones, etc.