Moving charge is the source of magnetism
Every magnetic field you’ve ever encountered — from a refrigerator magnet to Earth’s own field — ultimately comes from moving electric charge. In a bar magnet, it’s the coordinated motion of electrons within atoms; in an electromagnet, it’s current flowing through a coil of wire.
A moving charge creates a magnetic field around it, and that field then exerts a force on other moving charges nearby — magnetism, unlike gravity or the electric force, only acts on charges that are already in motion.
The reverse trick: making electricity from magnetism
Here’s where it gets genuinely useful: if a moving charge can create a magnetic field, a changing magnetic field can push charges into motion — generating an electric current. This is electromagnetic induction, discovered by Michael Faraday, and it’s arguably one of the most economically important discoveries in the history of physics.
Move a magnet through a loop of wire (or move the wire through a magnetic field), and a current appears in the wire, with no battery required. The faster the magnetic field changes, the stronger the induced current.
Why this one idea powers civilization, almost literally
Nearly all electricity generated worldwide — from coal plants, nuclear plants, wind turbines, hydroelectric dams — works the same fundamental way: something spins a magnet (or coil of wire) to continuously change a magnetic field, inducing current. Solar panels are the major exception, working through a different (photoelectric) effect.
Why this matters
Electricity and magnetism turning out to be two faces of the same underlying force — called electromagnetism — was one of the great unifications in physics history, eventually shown mathematically by James Clerk Maxwell in the 1860s. That same unification is also what predicts that light itself is an electromagnetic wave, tying together electricity, magnetism, and optics into a single framework.