What is Varistor?
[[File:Varistor S14K385 photo.jpg|thumb|Varistor]] [[File:VDRpiirrosmerkki.png|thumb|Symbol]] A '''varistor''', VDR, ''(voltage dependent resistor)'' is a type of resistor. It controls the [[electric current|current]] depending on the [[voltage]]. In these devices resistance drops sharply at a certain [[threshold voltage]]. Once the voltage across the device reaches the threshold, there is a [[Electrical breakdown|breakdown]] of the electrical structure in the vicinity of the [[grain boundary|grain boundaries]], which results in its [[electrical resistance]] dropping from several megohms down to a few hundred [[Ohm (unit)|ohm]]s. The major advantage of these is that they can dissipate a lot of energy, and they self reset–after the voltage across the device drops below the threshold, its resistance returns to being high. This makes them ideal for [[Surge protector|surge-protection]] applications. As there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in [[electrical substation]]s, where they are employed to protect the infrastructure from [[lightning]] strikes. They have rapid response, are low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application. They can be used to protect electronics from voltages that could damage components. {{Commonscat}} [[Category:Electronic components]] {{sci-stub}}