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Longman Dictionary of Contemporary English
impedance
noun
COLLOCATIONS FROM CORPUS
■ ADJECTIVE
high
▪ This provides a relatively high input impedance looking into their bases and a low output impedance at the emitters.
▪ Its high input impedance means that it does not load a signal source which it copies at its output.
■ NOUN
input
▪ This provides a relatively high input impedance looking into their bases and a low output impedance at the emitters.
▪ The input impedance also deteriorates at high frequencies.
▪ At low-enough frequencies to satisfy, the input impedance is virtually which is becoming very large.
▪ The term iterative impedance is applied to a load that renders the input impedance of an asymmetric section equal to it.
▪ Negative series-inserted feedback always raises the input impedance while negative shunt-inserted feedback reduces it.
▪ Its high input impedance means that it does not load a signal source which it copies at its output.
output
▪ Finally, is the small-signal, complex, output impedance when the input is open circuit to signals.
▪ This provides a relatively high input impedance looking into their bases and a low output impedance at the emitters.
▪ The output impedance is about 0.02 ohm at the 5V end and 0.1 ohm at the 15V end of the range.
EXAMPLES FROM CORPUS
▪ Ideally, any alternating voltmeter should possess infinite impedance and any a.c. meter negligible impedance.
▪ Its high input impedance means that it does not load a signal source which it copies at its output.
▪ Parameters and are in fact dimensionless while and respectively exhibit impedance and admittance dimensions.
▪ The impedance of the battery alone is enough to regulate their input.
▪ The output impedance is about 0.02 ohm at the 5V end and 0.1 ohm at the 15V end of the range.
▪ The phasors representing the e.m.f. and potential difference across impedance Z then have lengths in the same proportion to and respectively.
▪ Transformer coupling of the source and/or detector to the Wheatstone network is often adopted to match impedance levels or for isolation purposes.
The Collaborative International Dictionary
Impedance

Impedance \Im*ped"ance\, n. [Impede + -ance.] (Elec.) 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 root R^{2 + X^ 2}, where R = ohmic resistance, X = reactance. For an inductive circuit, X = 2[pi]fL, where f = frequency and L = self-inductance; for a circuit with capacity X = 1 [div] 2[pi]fC, where C = capacity.

Douglas Harper's Etymology Dictionary
impedance

1886, from impede + -ance.

Wiktionary
impedance

n. 1 (label en physics) A measure of the opposition to the flow of an alternating current in a circuit; the aggregation of its resistance, and inductive and capacitive reactances; the ratio of voltage to current treated as complex quantities. 2 (label en physics) A quantity analogous to electrical impedance in some other energy domain 3 # (label en physics usually with “mechanical”) a measure of opposition to motion of something subjected to a force; the ratio of force to velocity treated as complex quantities. 4 # (label en physics usually with “acoustic” or “sound”) the ratio of sound pressure to volume flow rate treated as complex quantities. 5 (label en by analogy software engineering usually with “mismatch”) a measure of the opposition caused by differences between two paradigms, especially between object-oriented development and relational databases

WordNet
impedance

n. a material's opposition to the flow of electric current; measured in ohms [syn: electric resistance, electrical resistance, resistance, resistivity, ohmic resistance]

Wikipedia
Impedance

Impedance is the complex-valued generalization of resistance. It may refer to:

  • Acoustic impedance, a constant related to the propagation of sound waves in an acoustic medium
  • Electrical impedance, the ratio of the voltage phasor to the electric current phasor, a measure of the opposition to time-varying electric current in an electric circuit
    • Characteristic impedance of a transmission line
    • Impedance (accelerator physics), a characterization of the self interaction of a charged particle beam
    • Nominal impedance, approximate designed impedance
  • Mechanical impedance, a measure of opposition to motion of a structure subjected to a force
  • Wave impedance, a constant related to electromagnetic wave propagation in a medium
    • Impedance of free space, a universal constant and the simplest case of a wave impedance
Impedance (accelerator physics)

Impedance in Accelerator Physics is a quantity that characterizes the self interaction of a charged particle beam, mediated by the beam environment, such as the vacuum chamber, RF cavities, and other elements encountered along the accelerator or storage ring.

Usage examples of "impedance".

Men in cargo hauler jumpsuits unloaded the sealed packages of replacement computerware: perfectly sandwiched circuits grown in orbit, sapphire films laid down in impedance paths on wafers, then sliced into specially patterned chips that followed old templates from Earth.

Techs immediately started integrating the sensors and tuning the impedances of the stasis flanges.

The linemen had fussed with multimeters and muttered about impedances and capacitances.