Comment Re:Not negative resistance (Score 5, Interesting) 123
Negative differential resistance just means that the current goes down when you increase voltage.
Interestingly, the entire electric grid is developing NDR, and that is a big problem for power companies. In the old days, if there was too much demand for electricity, or if transformers were overheating, the power company could reduce the voltage (a "brown-out") and the current would fall. But with more and more switching power supplies in electronics and fluorescent lights, that doesn't work as well anymore. The switching power supply in your computer and CFLs will compensate for reduced voltage by increasing the duration of the "on" phase of the switch, thus drawing additional current, the opposite of normal resistance.