Eddy
▸ noun: a
current of
water or air
? that moves against the main
current in a circular pattern
▸ verb: if a
current of
water or air
? eddies, it moves against the main
current in a circular pattern
▸ noun: a miniature whirlpool
? or whirlwind
? resulting when the
current of a fluid doubles back on itself
Eddy currents (also called Foucault currents
?) are currents induced in conductors, when a
conductor is exposed to a changing
magnetic field due to relative
motion of the field source and
conductor; or due to variations of the field with
time. This can cause a circulating flow of
electrons, or a
current, within the body of the
conductor. These circulating eddies of
current have
inductance and thus induce magnetic fields. These fields can cause repulsive
?,
attractive propulsion and drag effects. The stronger the applied
magnetic field, or the greater the electrical
conductivity of the
conductor, or the faster the field changes, then the greater the currents that are developed and the greater the fields produced.
The term
eddy current comes from analogous currents seen in water when dragging an oar breadthwise: localised areas of turbulence
? known as eddies give rise to persistent
vortices.
Eddy currents, like all electric currents, generate
heat as well as electromagnetic forces. The
heat can be harnessed for induction heating. The electromagnetic forces can be used for
levitation, creating movement, or to give a strong braking effect.
Eddy currents can also have undesirable effects, for instance power loss in
transformers. In this application, they are minimised with thin plates, by lamination of conductors or other details of
conductor shape.
Self-induced
eddy currents are responsible for the skin effect
? in conductors. The latter can be used for
non-destructive testing of materials for geometry features, like micro-cracks. A similar effect is the proximity effect, which is caused by externally-induced eddy currents
?. (wikipedia)
See Also
14.04 - Thirds as Currents
Current
Disturbance
Levitation
Vibration
Vortex
Wave