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# impedance

[ im-**peed**-ns ]

## noun

*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- 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.

impedance

/ ɪmˈpiːdəns /

## noun

- 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
- a component that offers impedance
- 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
- 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 /

- 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

impedance

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

## Notes

*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 impedance^{1}

## Example Sentences

There are a few factors that can affect a wire’s resistance, including length, thickness, and impedance.

We’ll walk you through terms like impedance, gauge, and resistance, followed by some products we stand behind.

A good EEG signal should have less than 50 kilo-Ohms of impedance.

In applying Ohm's law to an alternating current circuit, impedance must be substituted for resistance.

Find the reactance of a choke coil having a resistance of 10 ohms, when its impedance is 50 ohms.

In all such cases the impedance which the circuit offers is made up of two things—resistance and inductance.

The battery supply to the operator's transmitter is through an impedance coil 9.

These conditions are satisfied by using in the impedance coil many turns of large wire and an ample iron core.

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