The notion of impedance : definition
In the harmonic domain, the behavior of two terminal networks depends on frequency. The impedance of an electrical two terminal network in the harmonic domain is:
,
where
is the current flowing through the network, and
the voltage drop across it. The impedance therefore measures the reaction of a network to the current
flowing through it.
The impedance is a complex number:
Its magnitude is the ratio of the current and voltage magnitudes.
Its phase is a measure of the delay between the voltage and current at a certain frequency.
