Opposition to the flow of alternating current. Impedance has two aspects: resistance, which impedes both direct and alternating current and is always greater than zero; and reactance, which impedes alternating current only, varies with frequency, and can be positive or negative. See also resistance.
The total opposition to electrical flow (resistive plus reactive).
Electricity, apparent resistance to flow of alternating current.
The total opposition of a circuit to the passage of alternating electric current. It has the symbol Z. For an alternating current (AC) it includes the reactance X (caused by capacitance or inductance); the impedance can then be found using the equation Z2 = R2 + X2.
In acoustics, impedance refers to the ratio of the force per unit area to the volume displaced by the surface across which sound is being transmitted.