Impedance Control PCB

Impedance is the sum of the resistance and reactance of an electrical circuit expressed in Ohms. The resistance being the opposition to current flow present in all materials.

The reactance is the opposition to current flow resulting from the effect of the inherent capacitance and inductance of the conductor interacting with changes in voltage and current. In DC circuits there is no reactance and the resistance of copper conductors is typically insignificant.