Impedance

Impedance is the complex-valued generalization of resistance. It may refer to:


 * Acoustic impedance, a constant related to the propagation of sound waves in an acoustic medium
 * Electrical impedance, the ratio of the voltage phasor to the electric current phasor, a measure of the opposition to time-varying electric current in an electric circuit
 * High impedance, when only a small amount of current is allowed through
 * Characteristic impedance of a transmission line
 * Impedance (accelerator physics), a characterization of the self interaction of a charged particle beam
 * Nominal impedance, approximate designed impedance
 * Impedance matching, the adjustment of input impedance and output impedance
 * Mechanical impedance, a measure of opposition to motion of a structure subjected to a force
 * Wave impedance, a constant related to electromagnetic wave propagation in a medium
 * Impedance of free space, a universal constant and the simplest case of a wave impedance