Definition
A circulating loop of electrical current induced within a conductor when it is exposed to a changing magnetic field. Eddy currents flow in closed paths inside the metal itself, generate their own opposing magnetic field, and produce heat and drag as a byproduct. In aircraft systems they are deliberately used in some inspection and braking applications, and deliberately suppressed in others such as transformer and magneto cores by laminating the metal to break up the current paths.
Plain English
A small swirl of electricity that forms inside a piece of metal when a magnetic field near it changes. The swirl creates heat and a slight drag on whatever caused the change.
Context Anchor
Seen in aircraft electrical equipment, ignition and generator discussions, and maintenance inspections that use eddy currents to find flaws in metal parts.
Derivation
‘Eddy’ comes from an old word for a small whirlpool or swirl of water moving against the main current. The term was borrowed for electricity because these induced currents swirl in loops inside the metal, much like water eddies in a stream.
Why Pilots Care
Eddy current testing finds hidden cracks in critical metal parts without damaging them, directly supporting airworthiness and safety.
Grounding Statement
Picture moving a magnet quickly past a thick piece of aluminum. Tiny loops of electricity spin up inside the aluminum, warm it slightly, and resist the magnet’s motion. That resistance and warmth is the eddy current at work.
Intuition Check
Do not read eddy current as an air current or a normal wire current. Here it means a small circular electric flow inside a conductive material.
Example Sentence 1
The transformer core is made of thin laminated steel sheets to reduce eddy current losses and keep the unit from overheating.
Example Sentence 2
Laminated cores in magnetos reduce unwanted eddy currents that would otherwise waste energy as heat.