Magnetic reluctance

The magnetic resistance or reluctance Rm is the proportionality factor between the voltage and the magnetic magnetic flux Φ in the form:

The equation is referred to as the Hopkinson by John Hopkinsonsche law and has a shape similar to the Ohm's law to the electrical circuit, when the magnetic flux Φ to the electric current I and the magnetic potential is set in order for the electrical voltage U in analogy. The magnetic resistance is not to be confused with the magnetoresistive effect, which describes an electrical resistor, which is affected by a magnetic flux.

Due to the historically contingent concept formation the magnetic voltage Um in the literature is sometimes referred to as the magnetic flux with the symbols Θ.

The magnetic resistance for an element with a uniform magnetic flux equal to the size:

This corresponds to

In magnetic circuits with partially constant magnetic conductance, cross-sections and lengths magnetic resistance elements can be determined by the above relationship. The calculation rules for combining these resistors are analogous to the series and parallel circuit of electrical resistors.

The total resistance in the magnetic circuit is also decisive for the inductance L and Magnetic flux density B.

Magnetic resistors are used in the theory of magnetic circuits, which was developed by John Hopkinson and his son Edward Hopkinson at the end of the 19th century. The ideas developed at that time were a basis for the construction of electrical machines and are used for understanding of simple magnetic circuits today.

The reciprocal of the magnetic resistance, the magnetic conductivity or permeance Gm.

The unit of the magnetic resistance Rm is in the SI system is the reciprocal of the Henry unit and can be expressed as H-1. The unit of the magnetic conductance Gm is the Henry.