English: An IV curve (characteristic curve) of an electrical component with negative static resistance (red region). Static resistance corresponds to the usual definition of resistance, the voltage divided by the current

${\displaystyle R_{\text{static}}={v \over i}\,}$

Ordinary passive electrical components have positive static resistance and their IV curve is confined to the 1st and 3rd quadrants of the IV plane; only power sources and circuits producing electric power can have negative static resistance, indicated by portions of the IV curve in the 2nd or 4th quadrants of the IV plane. In the diagram, ${\displaystyle v<0\,}$ and ${\displaystyle i>0\,}$ so ${\displaystyle R_{\text{static}}<0\,}$