impedance

[im-peed-ns]

noun

1. Electricity.,  the total opposition to alternating current by an electric circuit, equal to the square root of the sum of the squares of the resistance and reactance of the circuit and usually expressed in ohms. Z

2. Also called mechanical impedance. Physics.,  the ratio of the force on a system undergoing simple harmonic motion to the velocity of the particles in the system.

3. something that impedes; an obstacle or hindrance.

impedance

/ ɪmˈpiːdəns /

noun

1. Z. a measure of the opposition to the flow of an alternating current equal to the square root of the sum of the squares of the resistance and the reactance, expressed in ohms

2. a component that offers impedance

3. Also called: acoustic impedance.  Za. the ratio of the sound pressure in a medium to the rate of alternating flow of the medium through a specified surface due to the sound wave

4. Also called: mechanical impedance.  Zm. the ratio of the mechanical force, acting in the direction of motion, to the velocity of the resulting vibration

impedance

1. A measure of the opposition to the flow of alternating current through a circuit. Impedance is measured in ohms. The resistance of a circuit to direct current (also measured in ohms) is generally not the same as its impedance, due to the effects of capacitance and induction in and among the components of the circuit.

2. See also impedance matching

impedance

1. A measure of the apparent resistance posed by an electrical circuit to an alternating current (AC).

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

Other Word Forms

• self-impedance noun

Word History and Origins

Origin of impedance¹

1886; impede + -ance; term introduced by O. Heaviside

Example Sentences

Pulse wave velocity was measured by impedance cardiography, while carotid intima-media thickness and carotid artery distensibility were measured by carotid ultrasonography.

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Martin is a multifaceted talent in the studio, as well versed in terms like “impedance” and “gain staging” as he is with microphones and composition.

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One of the resonators enables the light coming from the laser to couple with the other resonator; rather like impedance matching in electronics.

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Then there are people whose acid reflux is severe, as measured by the pH impedance study, and despite taking PPIs correctly, still experience painful, breakthrough heartburn.

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That’s similar to what I get on other bioelectric impedance devices but counter to everything my doctor told me at my last physical.

Read more on The Verge

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