Duality

In electrical engineering, electrical terms are associated into pairs called duals. A dual of a relationship is formed by interchanging voltage and current in an expression. The dual expression thus produced is of the same form, and the reason that the dual is always a valid statement can be traced to the duality of electricity and magnetism.

Here is a partial list of electrical dualities:

• voltage — current
• parallel — serial (circuits)
• resistance — conductance
• impedance — admittance
• capacitance — inductance
• reactance — susceptance
• short circuit — open circuit
• two resistances in series — two conductances in parallel;
• Kirchhoff's current law — Kirchhoff's voltage law.
• Thévenin's theorem — Norton's theorem

Examples

Constitutive relations

• Resistor and conductor (Ohm's law)

• Capacitor and inductor – differential form

• Capacitor and inductor – integral form

Voltage division — current division

Impedance and admittance

• Resistor and conductor

• Capacitor and inductor

See also

• Duality (electricity and magnetism)
• Duality (mechanical engineering)
• Dual impedance

References

• Turner, Rufus P, Transistors Theory and Practice, Gernsback Library, Inc, New York, 1954, Chapter 6.