Hello... The concept that resistance can be for a dc supply only and not for the ac supply coupled or superimposed to the same circuit, is something i don't understand to this moment... I first realized this in diode systems... where i saw bulk resistance for DC and dynamic resistance for AC... This doesn't get into mind at all.. they were both derived from the same I-V characteristic curve but bulk resistance utilized the curve made to diodes third approximation, while that of AC was obtained from the normal real curve nature of diode I-V characteristics... Help on this...??