# impedance

[im-peed-ns]

- 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. Symbol: Z
- 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.
- something that impedes; an obstacle or hindrance.

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## Origin of impedance^{}

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

## Examples from the Web for impedance

### Historical Examples

#### What is the impedance if the voltage of the line is 115 volts?

PhysicsWillis Eugene Tower

#### Impedance, however, does not equal the sum of resistance and reactance.

PhysicsWillis Eugene Tower

#### The impedance of its secondary will be a quarter of this or 3,000 ohms.

Letters of a Radio-Engineer to His SonJohn Mills

#### The impedance of the coil I is changed by moving its adjustable core.

Cyclopedia of Telephony and Telegraphy, Vol. 2Kempster Miller

#### Impedance depends chiefly upon the frequency of alternation.

The Library of Work and Play: Electricity and Its Everyday UsesJohn F. Woodhull

## impedance

- 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 ohmsSymbol: Z
- a component that offers impedance
- Also called: acoustic 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 waveSymbol: Z a
- Also called: mechanical impedance the ratio of the mechanical force, acting in the direction of motion, to the velocity of the resulting vibrationSymbol: Z m

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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

## Word Origin and History for impedance

Online Etymology Dictionary, © 2010 Douglas Harper

## impedance

[ĭm-pēd′ns]

- 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. See also impedance matching.

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The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

## impedance

[(im-peed-ns)]

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

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## Note

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

The New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.