Definition
Imaginary lines used to represent the direction and strength of a magnetic field. They flow from the north pole of a magnet to the south pole outside the magnet, and from south to north inside it. Where the lines are closer together, the field is stronger.
Plain English
A way of drawing a magnetic field so you can see which way it points and how strong it is. Picture invisible curved lines looping out of one end of a magnet and back into the other.
Context Anchor
Seen in instrument flying when learning how magnetism affects the magnetic compass and other magnetic-sensing instruments.
Derivation
From Latin fluxus, meaning 'a flowing.' The lines were named this way because early scientists pictured the magnetic field as something flowing through space, even though nothing physically moves along them.
Why Pilots Care
Understanding lines of flux explains why the compass points toward magnetic north and why local magnetic disturbances produce heading errors.
Analogy
Think of lines of flux like wind arrows on a weather map. The arrows are not the wind itself, but they help you see which way the wind is moving and where it is stronger.
Grounding Statement
If you sprinkle iron filings on paper over a bar magnet, they line up in curved patterns from one pole to the other. Those patterns trace the lines of flux.
Intuition Check
Lines of flux are not visible strings, wires, or actual lines in the air. They are a way to picture the direction and strength of magnetic force.
Example Sentence 1
The compass needle aligns itself with the Earth's lines of flux, which is why it points roughly toward magnetic north.
Example Sentence 2
When an aircraft passes over iron-ore deposits, the lines of flux bend and the compass heading becomes unreliable.