impedance (redirected from reactance)

impedance /im·ped·ance/ (im-pēd´ans) obstruction or opposition to passage or flow, as of an electric current or other form of energy. Symbol Z .

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acoustic impedance  an expression of the opposition to passage of sound waves, being the product of the density of a substance and the velocity of sound in it.

aortic impedance  the sum of the external factors that resist ventricular ejection.

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impedance

[impē′dəns]

Etymology: L, impedire, to entangle

a form of electric resistance observed in an alternating current that is analogous to the classic electric resistance that occurs in a direct current circuit. It is expressed as a ratio of voltage applied to a circuit to the current it produces, as an alternating current oscillates ahead of or behind the voltage.

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impedance

obstruction or opposition to passage or flow, as of an electric current or other form of energy.

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acoustic impedance

an expression of the opposition to passage of sound waves, being the product of the density of a substance and the velocity of sound in it.

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Impedance

Cardiac pacing The total opposition that a circuit presents to alternating electrical current. Cf Resistance.