How can a permanent magnet be demagnetized?
cut the magnet in half
heat the magnet up (my choice)
strike the magnet with a heavy blow
both the second and third choices above
To demagnetize a permanent magnet, one effective method is to heat it up. Here's an explanation of why heating a magnet can demagnetize it:
Permanent magnets are made up of tiny magnetic domains, which are groups of atoms with aligned magnetic fields. In a magnetized state, these domains are all properly aligned, resulting in a strong magnetic field. However, when the magnet is heated, the thermal energy disrupts the alignment of these magnetic domains. As the temperature increases, the atomic vibrations become more intense, causing the domains to lose their alignment. This randomizes the magnetic field, effectively demagnetizing the material.
Another option mentioned in the question is to strike the magnet with a heavy blow. While this can potentially cause some disruption to the alignment of the magnetic domains, it is not as reliable or controlled as heating. Similarly, cutting a magnet in half may also disrupt the alignment of the domains to some extent, but it is not a guaranteed demagnetization method.
Therefore, in this case, the most effective choice to demagnetize a permanent magnet is to heat it up.