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Opposite of a resistor Answered

So a resistor reduces the current, what would increase the "speed" of the current? Is there such thing?



5 years ago

i am looking for something simliar.
my application is kinda like a pressure sensor

basically im trying to design a device that the harder some one presses on the "pressure sensor" the faster an array of dc vibrators rotate.

so its transfering pressure into vibrations by increasing energy to the motors.

any ideas?

You posted this as a question -- did you see Steve's response?

What you're looking for is a transducer, which will convert some mechanical signal (in this case pressure), into a varying quantity like voltage.

.  There is no opposite of resistance. There is the seimen (mho, for us old guys), but that is the reciprocal of resistance, not its opposite.
.  I don't think gmoon's transconductance applies here (I've only seen the term used in reference to amplifiers), but I don't know enough about transconductance to say that with any confidence.

Conductance is 1/R, and it's also resistance (E/I) flipped, or I/E. Transconductance is a ratio of the input voltage to the output current. Devices with transconductance are "active," and complex compared to a resistor, and a small input change can control (amplify) a large amount of current.

Transconductance is perhaps too limited a description of the "opposite of resistance" because it describes only one aspect or metric of "amplification," rather than amplification in general.

I still stand by "the opposite of a resistor is something that amplifies current."

If the range of all possible resistances is from infinite resistance (so far below unity that it's unmeasurable) to zero resistance (unity), then the opposite is "above unity" -- or a device that amplifies. At least how I look at it ;-)

.  That sounds good, but something about it just doesn't feel right to me. But, as I said, I really don't understand it. I'd say there's at least a 50/50 chance that we are both wrong. ;)
.  Doesn't really matter. Looks like the OP is really worried about power and not resistance or current, per se.

The problem with my "solution" is it's a "practical opposite," not a purely conceptual one.

It's like saying the opposite of gravity is the force of kinetic energy in an opposing vector. Yes, kinetic energy can counteract gravity, but it's not it's theoretical opposite.

If we could figure out what "opposite" means here, that would help.

It's the best I can do, though, sorry.

On the other hand, mathematically you could model the "opposite" (depending on your definition) and build a "transconductor" from a transistor and a couple discrete components. Neither the "transconductor" or the resistor is completely "enclosed" in the circuit. The "transconductor" would need a separate current source to achieve "above unity", and the resistor achieves "below unity" by dissipating heat externally...

The actual electrical response of resistors isn't "pure" either--their characteristics change with heat, etc. And you could "complex up" the resistor--a POT, for instance.

Just musing, at this point ;-)

Your problem is that you're not storing enough charge. Suggestions:
Increase capacity with bigger capacitor(s)
Increase charge time
Can you give us a circuit diagram for this device?


 Thanks guys for all your comments! The reason I was wondering is because in my engineering class, we are making solar powered cars that run on a basic DC motor and a .42 volt solar panel. I tried using capacitors to hold a charge for the shade spots(it like an obstacle course) and its not very fast so that why I was wondering if there was a way to "speed up" the current.
And thanks again for not calling me a "noob" or novice, even though I am. Im only 16 so yeah, Thanks again though!

Electricity flows at the speed of light so I think resistors are only restricting the flow so it is like a valve.  Open it all the way up with no resistance and just more electricity flows through from the source. Superconductivity is a subject to look into on your question.

Electricity flows at much less than the speed of light, unfortunately.  The electrons in the wire are constantly scattering off of the metal atoms, so the current flow is actually a diffusive process.  There's a nice writeup I found linked to the Wikipedia stub "speed of electricity". 

In copper wire, the drift velocity is 4.62 (mm/s)/(V/m), where the normalizing denominator, volts per meter, measures the electric field which drives the electrons in terms of the applied voltage vs. the length of wire.

In a coaxial cable, the waves (microwaves, television, etc.) travel at about 2/3 c, even though the current itself is only flowing at a few mm/s.

Is Jell-O conductive?  It ought to be, with all the sugar, but I don't have any data.  In any event, you'll get a different answer in Jell-O than in copper.  It depends on the density of states (number of free electrons vs. scattering centers).

But if I drop a chunk into a vat of liquid nitrogen I might find some interesting properties.


8 years ago

The opposite of resistance is transconductance.

So the opposite of a resistor is something that amplifies current--like a transistor (which got it's name from "transconductance varistor".)