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. 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 Z
2. a component that offers impedance
3. Also calledacoustic impedance 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 Za
4. Also calledmechanical impedance the ratio of the mechanical force, acting in the direction of motion, to the velocity of the resulting vibration Zm

impedance

/ ĭm-pēd′ns /

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) .

Notes

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

Other Words From

• self-im·ped·ance 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.

From Science Daily

An additional step could include estimating visceral fat through a bioelectrical impedance weighing scale, which passes a small electrical current through the body to estimate fat quantities; it’s cheaper but admittedly less precise than full-body imaging scans.

From Slate

Thanks to excellent impedance matching between stages, the amplifiers demonstrated outstanding performance, as Prof. Okada highlights: "The proposed power amplifiers achieved a gain higher than 20 dB from 237 to 267 GHz, with a sharp cut-off frequency to suppress out-of-band undesired signals."

From Science Daily

"Because phase angle can be measured even by impedance analyzer for home use, such as weighing scales with body composition analyzer, phase angle may be the way to monitor muscular health easily and quickly. If possible, segment-level phase angle measurement can be conducted even by impedance analyzer for home use," says Prof. Akagi.

From Science Daily

The graphene microelectrodes exhibit low impedance and high charge injection, essential attributes for flexible and efficient neural interfaces.

From Science Daily

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