Question

How does resistance differ from impedance?

Answer 1

Resistance is the opposition imposed on a current (Direct or alternating) by a conductor itself. It increases with temperature due to increased energy of the charge carriers.

But, in some alternating current circuits, where inductive and capacitative elements are present, they in addition offer an extra opposition to the flow of current due to the fact that they store magnetic and electrical energy respectively. This obstruction is quantitatively given by inductive reactance (`X""_L`) and capacitative reactance (`X""_C`).

The net effect of the three factors determine the net obstruction the circuit offers to the current flow and is called the impedence of the circuit. It is mathematically expressed as,

`Z = [ R^2 + (X""_C - X""_L)^2]^(1/2)`