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# Opposite of a variable resistor is there such a thing as a variable conductor? Answered

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## 6 Replies

steveastrouk (author)2010-03-18

It isn't the opposite ! You can define a unit called conductance, which is 1/resistance. It has the SI unit of the Siemen. 1000 Ohms is 1mOhm, 100 Ohms is 0.01 Siemens, 1 Ohm is 1 Siemen.

If you want to imagine a potentiometer calibrated in Siemens instead, you have a variable conductance.

gmoon (author)2010-03-18

Right on--transconductance is also a unit of conductivity.

Conductivity used to be labeled as units of mho ("ohm" spelled backwards) before they changed the name to "Siemens."

As in 0.05 mhos. Or 4000 micromhos. You'll see "mhos" in a lot of older books...

lemonie (author)2010-03-18

You didn't mean inductor did you?

L

jeff-o (author)2010-03-18

It's the same thing!  If you want an actual voltage or current gain, you'll need an amplifier.  A transistor might be all you need.

philgenius (author)2010-03-18

No.

If there was, it would do the same thing as a variable resistor.

Variable resistors can change their resistance based on the position of a dial or a slide. Variable conductors (theoretically, according to what you are asking) would change their conductivity based on the position of a dial or a slide. Both are basically the same. To reduce conductivity, increase resistance, and vice versa.

If you want a "variable conductor", just get a variable resistor with a really small max. resistance.

Re-design (author)2010-03-18

Well a resistor is also considered a variable conductor, since the conduction of it varies inversely with the resistance.

But some transistor is a variable conductor.  The more voltage applied to it, the more it conducts.

Simply put, but there is more to it than that.