Impedance is the complex-valued measure of opposition that a circuit element or network presents to sinusoidal current at a given frequency. Parameters: (1) resistance R (real part, frequency-independent opposition from dissipation), (2) reactance X (imaginary part, frequency-dependent opposition from energy storage in capacitors and inductors), (3) frequency f (the sinusoidal excitation frequency at which Z is evaluated). The magnitude |Z| determines current amplitude for a given voltage; the phase angle determines current lag or lead. Persistence mechanism: mathematical formalism codified in circuit theory, embedded in engineering practice, simulation tools (SPICE), and educational curricula. [formal: impedientia | substrate: mind | horizon: as-long-as-us | explicit: yes | epoch: 0.10]
Accepted ontology entry
impedance
Impedance is the complex-valued measure of opposition that a circuit element or network presents to sinusoidal current at a given frequency. Parameters: (1) resistance R (real part, frequency-independent opposition from dissipation), (2) r…
Definition
Why it is in scope
A human-made analytical concept in electrical engineering that extends the notion of resistance to alternating-current (AC) circuits by representing opposition to current as a complex quantity — real part resistance, imaginary part reactance — which varies with frequency. Built to characterize and predict how circuit elements and networks respond to time-varying signals.
Names and aliases
- impedanceen · CANONICAL
Relations from this entry
- cmrhs7rba02ak8aeh9cyz8tsrDERIVED_FROM →
Resistance (DC opposition to current) existed first. Impedance extends this concept to AC circuits by adding frequency-dependent reactance as the imaginary component. The historical and conceptual lineage is clear: resistance is the special case of impedance at zero frequency.
- cmrc6dopv00jba9g4op1ivbb1SERVES →
Impedance matching is deliberately designed to ensure reliable signal transmission in communication systems — preventing reflections and power loss. The designed purpose of impedance management is to further communication operation. Per Law 8d: teleological relation, servant (impedance)→master (communication).
- cmsp7463504cajlssidwwmljjCONTAINS →
Impedance is a complex quantity Z = R + jX, decomposed into two constituent parts: resistance (real) and reactance (imaginary). Reactance is literally one of the two parts that make up impedance as a whole — a structural decomposition, not an incidental property. CONTAINS is the right arrow (whole→part, Law 10).
- cmrc361dn0082a9g46bcbfpitINSTANCE_OF →
impedance IS a specific kind of property: it is the measure of opposition to current flow in an electrical circuit. A competent speaker in electronics would call impedance a type of property — specifically, an electrical property. Ladder: property is the nearest general kind.
Relations to this entry
- cmsp7463504cajlssidwwmljj← INSTANCE_OF
Reactance is the imaginary part of impedance — a specific kind of impedance component (frequency-dependent opposition to AC current). A competent speaker calls it 'a kind of impedance behavior'. Per Law 9, nearest kind.
Record identity
- Created
- Aug 11, 2026, 9:31 PM UTC
- Content hash
- 63445fa9fc51adf653e13fe6ce16bcb7f75c2c821d45a908b814d181d10ee6de