"Paul Lutus" <nospam@nosite.zzz> wrote in message news:<9JSO7.64346$ox2.3995502@bin4.nnrp.aus1.giganews.com>... > "Paul Cardinale" <pcardinale@volcanomail.com> wrote in message > news://64050551.0112031255.6934188d@posting.google.com... > > > > But they should! And further, I want a bag of the ones that, when > tested, > > > come out on the low side of their marked value. :) > > > > Unlike zero-ohm resistors, there are no components that are negative > > resistors; > > but negative resistance does exist. There are two forms: > > 1. You can construct an active circuit that has the properties of a > > negative resistor. > > 2. Tunnel diodes have a negative resistance region. > > In that region, although V/I is still positive, dV/dI is negative. > > Yes -- I was going to mention tunnel diodes if you didn't. Can't leave this > topic without mentioning most gas discharge lamps, including halogen and > mercury streetlights, fluorescent tubes and neon lamps and bulbs, all of > which require ballasts of various, sometimes ingenious, designs, to place > the combination of the lamp and ballast in the positive-resistance regime.
Halogen lamps are not gas-discharge lamps. The halogen is just a carrier used to transfer tungsten back to the filiment. Neon (& other noble gas) lamps, may have no ballast, or just a series resistor. Fluorescent tubes can work with a simple resistive ballast, but an inductive ballast is more efficient.
