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Magnetic reluctance is the resistance of a material to a magnetic field. It is defined as the ratio of magnetomotive force (SI unit: ampere-turns) to magnetic flux (SI unit: weber).
The reluctance R of a uniform magnetic circuit can be calculated as:
- <math>R = \frac{l}{\mu A}<math>
where
R is the reluctance, measured in ampere-turns per weber. This unit is equivalent to the reciprocal henry (<math>H^{-1}<math>) multiplied by the number of turns
l is the length of the circuit, measured in metres
μ is the magnetic permeability of the material, measured in henry per metre (<math>H.m^{-1}<math>)
A is the cross-sectional area of the circuit, measured in square metres
Applications
The variation in the reluctance of a magnetic circuit, in which part of the circuit is moving, is used in measuring instruments called reluctance sensors.
Increasing the reluctance of a magnetic circuit enables it to store more energy. This effect is used in the flyback transformer.
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