Recommended
How Special Relativity Makes Magnets Work
Why people recommend it
Veritasium explains why magnetism falls out of special relativity, linked when people ask what magnetic fields really are.
Watch for: Conceptual physics rather than practical circuit design
In their words
Another way to ponder how strong these forces are: magnetic forces (in an electromagnet, for example) can be explained by relativistic contraction of electrons due to their movement from the current in the coil, even when that speed is on the order of 10 cm per hour.
Phil Frost on electronics.stackexchange.com, May 2017. CC BY-SA.
