Flux is commonly visualized as magnetic lines passing through a given area.

The words magnet and magnetism are derived from the Greek word "magnetite". Magnetite, a magnetic oxide of iron, was mined in Magnesia and mentioned in Greek texts as early as 800 BC. Thales of Miletus (640-547 BC), who lived nearby, was the first to study magnetic forces. He knew that magnetite attracts iron and that rubbing amber (a fossil tree resin that the Greeks called elektron) would make it attract lightweight objects such as feathers.

Not much was learned about magnetism until 1819 when Hans Oersted (1777-1851) passed an electrical current through a wire and noticed that a nearby compass needle deflected. This stimulated a great interest in magnetism and led to rapid advances.

Michael Faraday (1791-1851) conceptualized most of the electro-magnetic concepts. James Maxwell (1831-1879) expressed Faraday's concepts mathematically and expanded upon them to include dielectric displacement, permeability, electro-magnetic radiation and so on.