> (since resistance is DC) Resistance is actually a frequency-dependent quantity as well. It's the component of impedance that dissipates power (ie, current an

> (since resistance is DC) Resistance is actually a frequency-dependent quantity as well. It's the component of impedance that dissipates power (ie, current and voltage are in phase). A very simple example of a frequency-dependent resistor is a solid copper wire. DC currents flow through the whole cross-sectional area; AC currents flow through an area that excludes an increasing fraction of the interior as the frequency increases. Magnetic hysteresis and eddy current losses also behave as frequency-dependent resistances (although you might alternatively think about the latter as a frequency dependent coupling to a resistor).