Analogy of electrical and magnetic quantities

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The analogy of electrical and magnetic quantities is a consequence of the strong symmetry in Maxwell's equations between the electrical and magnetic quantities that occur. These analogies are helpful for understanding electromagnetic and electrotechnical relationships and phenomena and are often given in textbooks.

The sizes of the stationary flow field have a strong analogy to fluid mechanics and thermodynamics and can be explained quite clearly (see also electro-hydraulic analogy ). The magnitudes of the electrostatic and magnetic fields are rather abstract, but can be well understood using the analogy. In addition, the difference between electric and magnetic fields (e.g. electric and magnetic monopoles , Lenz's rule ) becomes very clear in the analogies.

Electrical quantities Magnetic sizes
Electrostatic field Stationary flow field Magnetic field
Particulate swell size Electric charge

no source size known

(Fictional magnetic monopole )

Field strength Electric field strength

Magnetic field strength

Material parameters Permittivity

Specific conductance / resistance


Complex permittivity


Flux density quantity Electric flux density

Current density

Magnetic flux density

Flow size


Electric flow

Current (charge flow)

Magnetic river

Flow through volume Contained cargo

Integral set of nodes

Integral magnetic knot set

Node set 1. Kirchhoff's law

Magnetic node set


Field strength quantities

Electric voltage

Magnetic tension

potential Electrical potential

Magnetic potential

Integral swell size Electrical source voltage ( law of induction )

Magnetic source voltage (flooding)

Mesh sets 2. Kirchhoff's law

Magnetic mesh set

Energy density Electrical energy density

Power dissipation density

Magnetic energy density

Field energy Electric field energy

Magnetic field energy

Electrotechnical component capacitor resistance Inductance / coil
property capacity resistance Inductance
Definition equation capacity

Conductance / resistance


Design equation

from field sizes

Design equations

for a homogeneous field


Electrical conductance / resistance

Inductance / Magnetic Resistance


Magnetic resistance

Current-voltage relationship Ohm's law


  1. a b c d The magnetic flux results from the integration of the flux density over an area. In the case of a coil with one turn, this is precisely the area enclosed by the turn. The surface in coils with several turns is actually a screw or helical surface . Since these windings are usually permeated by one and the same magnetic flux, they are viewed as individual windings and the linked magnetic flux is defined in electrical engineering . This results in the additional parameters or , in accordance with most textbooks . For a turn or if the three-dimensional conductor geometry in a coil is actually correctly taken into account, the linked flux can be replaced by the magnetic flux and (see also magnetic flux ).

Individual evidence

  1. K. Lunze: Introduction to electrical engineering - textbook . Verlag Technik, 1988, ISBN 3-341-00504-8 .
  2. ^ E. Philippow: Fundamentals of electrical engineering . Verlag Technik, 2000, ISBN 978-3-341-01241-3 .