Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A measure of the total opposition to current flow in an alternating current circuit, made up of two components, ohmic resistance and reactance, and usually represented in complex notation as Z = R + iX, where R is the ohmic resistance and X is the reactance.
  • n. An analogous measure of resistance to an alternating effect, as the resistance to vibration of the medium in sound transmission.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A measure of the opposition to the flow of an alternating current in a circuit; the aggregation of its resistance, inductive and capacitive reactance. Represented by the symbol Z.
  • n. a measure of opposition to motion of something subjected to a force.
  • n. the sound pressure divided by the particle velocity and the surface area through which an acoustic wave propagates.
  • n. a measure of the opposition caused by differences between two paradigms, especially between object-oriented development and relational databases

from the GNU version of the Collaborative International Dictionary of English

  • n. The apparent resistance in an electric circuit to the flow of an alternating current, analogous to the actual electrical resistance to a direct current, being the ratio of electromotive force to the current. It is equal to R2 + X2, where R = ohmic resistance, X = reactance. For an inductive circuit, X = 2πfL, where f = frequency and L = self-inductance; for a circuit with capacity X = 1 ÷ 2πfC, where C = capacity.

from The Century Dictionary and Cyclopedia

  • n. Hindrance; specifically, in electricity, an apparent increase of resistance due to induction in a circuit.
  • n. Impedance is the apparent resistance of an alternating-current circuit, or the ratio of the electromotive force consumed by an alternating current, divided by the current. On account of the electromotive force consumed by self-induction, the apparent resistance with alternating currents is greater than that with direct currents, though the power-consumption is the same. The impedance consists of two components—resistance, which consumes power, and reactance, which is the wattless resistance due to self-induction. See resistance, 3, and reactance.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a material's opposition to the flow of electric current; measured in ohms

Etymologies

impede +‎ -ance (Wiktionary)

Examples

  • ‡ The term impedance is most often encountered in dealing with antennas and speakers in television, stereo, and radio systems.

    impedance

  • One of the problems the middle ear has to overcome is the mismatch in impedance between air and the cochlea, but impedance matching by the middle ear results in only a 30 dB increase in sound energy transmitted to the inner ear.

    A Decade Spanning Single Exchange

  • Guts: One of the problems the middle ear has to overcome is the mismatch in impedance between air and the cochlea, but impedance matching by the middle ear results in only a 30 dB increase in sound energy transmitted to the inner ear.

    A Decade Spanning Single Exchange

  • Yes, the difference in impedance would be fairly large.

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  • The phrase impedance matching seems to have moved towards mainstream language in recent times:

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  • When effective resistances and reactances are connected together, either in series or parallel or series-parallel, then the equivalent resistance of the overall circuit is called impedance Z.

    7. Alternating Current

  • The issue with the Thiels is they have low sensitivity (84dB, I believe for the 3.6) and impedance, which is rated at 4 ohm but may actually be as low as 3.

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  • The music reference hit home as well, as I often experienced this kind of impedance mismatch with the drummer from my old band - he's an inexhaustible fountain of music minutiae.

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  • Furthermore expertise in a number of relative applied techniques, such as impedance spectroscopy will also be vital.

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  • Note: For the purposes of this explanation the term "impedance" is synonymous with "electrical resistance".

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