|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 (ĭm-pēd'ns) Pronunciation Key
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.