What Is a Magnetic Field?
Steel filings on a magnet that show the magnetic field lines
Magnetic fields. Moving electric charges generate magnetic fields, which exert forces on other moving charges and on magnetic materials such as iron, nickel, and cobalt.
Visualizing the field. Steel filings reveal a magnetic field because each particle is ferromagnetic. Near a magnet, the field magnetizes and aligns the filings, creating curved patterns known as “field lines.”
What the pattern shows. The filings reveal three key features: field direction through their alignment, relative strength through their density, and overall shape through dipole patterns, loops between poles, and distortions caused by nearby materials.
