Magnetic reluctance can be thought of as having an analogous function to resistance in an electrical circuit except that it cannot consume energy. The term was coined in May 1888 by Oliver Heaviside. ^[1] The notion of “magnetic resistance” was first mentioned by James Joule ^[2] and the term "magnetomotive force” was first named by Bosanquet.^[3] Idea about an application to a magnetic flux the law, which is similar to Ohm's law for a closed electric circuit, is attributed to H. Rowland.^[4] Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... The article on electrical energy is located elsewhere. ... There are many kinds of circuit An electric circuit interconnects electrical elements or electronic elements together usually to perform some useful function. ... 1888 (MDCCCLXXXVIII) is a leap year starting on Sunday (click on link for calendar) of the Gregorian calendar or a leap year starting on Tuesday of the Julian calendar. ... Oliver Heaviside (May 18, 1850 – February 3, 1925) was a self-taught English engineer, mathematician and physicist who adapted complex numbers to the study of electrical circuits, developed techniques for applying Laplace transforms to the solution of differential equations, reformulated Maxwells field equations in terms of electric and magnetic... James Prescott Joule (December 24, 1818–October 11, 1889) was an English physicist, born in Salford, near Manchester. ... In physics, the magnetomotive force produces magnetic flux. ... Magnetic flux, is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... Ohms law states that, in an electrical circuit, the current passing through a conductor is directly proportional to the potential difference applied across them provided all physical conditions are kept constant. ... An electrical network or electrical circuit is an interconnection of analog electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. ...

It is equal to the ratio of the MMF in a passive magnetic circuit and the magnetic flux in this circuit or to the ratio of their amplitude values for a sinusoidal MMF and magnetic flux. It is a scalar value. A magnetic circuit is a closed path containing a magnetic flux. ... Magnetic flux, is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... Magnetic flux, is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... A scalar may be: Look up scalar in Wiktionary, the free dictionary. ...

Definition

The definition can be expressed as:

where

S is the reluctance in ampere-turns per weber (a unit that is equivalent to turns per henry)

F is the magnetomotive force (MMF) in ampere-turns

Φ is the magnetic flux in webers.

This is analogous to Ohm's Law with resistance replaced by reluctance, voltage by MMF and current by magnetic flux. Current can be measured by a galvanometer, via the deflection of a magnetic needle in the magnetic field created by the current. ... In physics, the weber (symbol: Wb) is the SI unit of magnetic flux. ... Look up Henry in Wiktionary, the free dictionary. ... Ohms law states that, in an electrical circuit, the current passing through a conductor is directly proportional to the potential difference applied across them provided all physical conditions are kept constant. ...

Magnetic flux always forms a closed loop, as described by Maxwell's equations, but the path of the loop depends on the reluctance of the surrounding materials. It is concentrated around the path of least reluctance. Air and vacuum have high reluctance, whilst easily magnetized materials such as soft iron have low reluctance. The concentration of flux in low-reluctance materials forms strong temporary poles and causes mechanical forces that tend to move the materials towards regions of higher flux so it is always an attractive force(pull). In electromagnetics, Maxwells equations are a set of four equations, compiled by James Clerk Maxwell, that describe the behavior of both the electric and magnetic fields, as well as their interactions with matter. ...

The reluctance of a uniform magnetic circuit can be calculated as:

where

l is the length of the circuit in metres

μ₀ is the permeability of free space, equal to henry per metre

μ_r is the relative magnetic permeability of the material (dimensionless)

A is the cross-sectional area of the circuit in square metres

The inverse of reluctance is called permeance. The metre, or meter (U.S.), is a measure of length. ... This article is in need of attention. ... A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ... Permeance is inverse of reluctance. ...

Applications

Air gaps can be created in the cores of certain transformers to reduce the effects of saturation. This increases the reluctance of the magnetic circuit, and enables it to store more energy before core saturation. This effect is also used in the flyback transformer. For magnetic materials, saturation is the state when the material can not absorb a stronger magnetic field, such that an increase of magnetization produces no significant change in magnetic flux density. ... A flyback transformer or line output transformer (LOPT) is a type of transformer used to generate the high voltage needed for driving a cathode ray tube or picture tube. It converts the input voltage, usually mains voltage in the range 120 to 240 volts, to an output voltage in the...

Variation of reluctance is the principle behind the variable reluctance generator and the Alexanderson alternator. An Alexanderson alternator is a rotating machine for the generation of high frequency with frequencies until 100 kHz. ...

Reluctance can also be applied to:

• Reluctance motors
• Variable reluctance (magnetic) pickups

Rotating magnetic field as a sum of magnetic vectors from 3 phase coils An electric motor converts electrical energy into kinetic energy. ... Pickup or pick-up may refer to: Pickup, a device which detects vibrations from music instruments Pickup truck, a light truck with an open-top rear cargo area. ...

References

1. ^ Heaviside O., Electrical Papers. Vol.2. – L.; N.Y.: Macmillan, 1892, p. 166.
2. ^ Joule J., Scientific Papers, vol. 1. – 1884, p. 36.
3. ^ Bosanquet, Phil. Mag., vol. 15, 1883, p. 205.
4. ^ Rowland H., Phil. Mag. (4), vol. 46, 1873, p. 140.