Dual (electronics)

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In electronics, the word dual refers to two devices or circuits that have mathematical descriptions that are identical except that voltages in one correspond to currents in the other, and vice versa. For example:

• a resistance is the dual of a conductance;
• two resistances in series are the dual of two conductances in parallel;
• a capacitor is the dual of an inductor;
• an electrostatic motor is the dual of a magnetic motor;
• Kirchhoff's current law is the dual of Kirchhoff's voltage law.

In physics, the Electromagnetic dual concept is based on the idea that, in the static case, Electromagnetism has two separate facets: electric fields and magnetic fields. Electric fields are the dual of magnetic fields, and vice versa. Also:

• Permittivity is the dual of permeability.
• Piezoelectricity is the dual of magnetostriction.
• Ferroelectrics (or electrets) are the dual of ferromagnets.
• Electrets are the dual of permanent magnets;
• The Faraday Effect is the dual of the Kerr effect.

For other meanings of the word not related to electronics, see dual.