I said I was guessing. Perhaps lowering the temperature of the resistor will force the resistance to drop. The needed resistance is 18KΩ, so IF IT IS POSSIBLE TO COOL THE RESISTOR "APPROACHING" SUPERCONDUCTIVITY, then to "Force" 1 mA through a 1 MegΩ resistor might require cooling it well below normal temperatures. If I used the term "Superconductor" it was to give an idea of where I was going with it. Cooling it MAY be the only way to force more curren through the resistor. But again - I'M GUESSING PEOPLE!

If we stick strictly with ohms law then we all should know it's not possible. "Should" meaning anyone who thinks it may be possible under conventional methods needs to study more about ohms law.

 

"a superconductor with a resistance of 18,000 Ω" is nonsensical.

Perhaps I should have used the term "Approaching that of a superconductor".

Then again, maybe it's not possible to turn a carbon resistor (or any other sort of resistive element) into (or approach that of a) superconductor.

 

No matter what you do to the circuit, you're not going to force more amperage through it. Parallel resistance means providing an alternative path around the main resistor. More current follows a different path (path of least resistance) but never will any more than 18 µA flow through that resistor with only 18 volts supplied. Just won't happen!

No matter what you do to the circuit? Even if he uses a DC-DC converter to take in 18 V and put out 1000 V?

 

I said I was guessing. Perhaps lowering the temperature of the resistor will force the resistance to drop. The needed resistance is 18KΩ, so IF IT IS POSSIBLE TO COOL THE RESISTOR "APPROACHING" SUPERCONDUCTIVITY, then to "Force" 1 mA through a 1 MegΩ resistor might require cooling it well below normal temperatures. If I used the term "Superconductor" it was to give an idea of where I was going with it. Cooling it MAY be the only way to force more curren through the resistor. But again - I'M GUESSING PEOPLE!

If we stick strictly with ohms law then we all should know it's not possible. "Should" meaning anyone who thinks it may be possible under conventional methods needs to study more about ohms law.

Even if cooling it resulted in a 56x lowering of the resistance, you would not be getting 1 mA through a 1 MΩ resistor because the resistor would now be 18 kΩ that just happens to have bands on it that indicate that it happens to be 1 MΩ under certain conditions that no longer apply.

None-the-less, what you are basically saying is that one way to get 1 mA through this physical thing that has been labeled a 1 MΩ resistor is to change the resistance of it. That's a valid point, but is almost certainly not what the TS will accept as a viable solution to his problem. Furthermore, cooling it is NOT the only way to force more current through the resistor -- you can also increase the voltage across it. It is unclear if this will be an acceptable solution for the TS's problem or not, because it is unclear what they meant when they said that they didn't want to change the voltage.

@RdAdr: It would be very helpful if the TS clarified what their constraints are.

 

Again I'm caught out by semantics. If we stay with 18 volts and 1 MegΩ the TS is going to only see 18µA.

Here's what I assumed the TS was asking: (and yes, I know how to spell assume) - take a single path circuit from an 18 volt source through R1 (1 meg ohm) and add something to the circuit - like adding a light bulb of some high wattage "IN SERIES", will that make it draw more current? The answer is "No, it won't." Even if you dead short the light bulb - not more than 18 µA will flow through R1. I can understand the reason for the question IF the TS is a beginner learning about electricity I probably wondered something similar at some long ago point in my life. Many awry ideas have run through my head. Having learned a little more about it - I can say that adding components (not power sources) to the circuit will never draw more than 18µA through R1.

IF we're going to consider CHANGING the power source (or boosting it) (which IS adding a component or two in parallel) then we can also consider changing the resistance by somehow degrading the resistive characteristics of R1. I'm no college professor here - and sometimes the correct terminology eludes me, but in the sense I got - adding any additional load (in series) will not draw any more current through R1. Adding circuitry parallel to R1 may draw more current from the power source but again, R1 remains largely unaffected as to how much current flows through it.

If we add R2 (1 meg) then we up the current in the circuit to 36 µA, but again, through R1 - it's still 18 µA. There are two paths for electrons to follow. half of them will flow through R1 and the other half through R2.

To force 1 mA through R1 the only way is to change the amount of voltage dropped across it. That will require upping that voltage to 1Kv. A buck converter (if one exists that can deliver that kind of power) would constitute an additional piece of circuitry to the project. However, again, the TS wanted 18 volts to produce 1 mA.

If freezing the resistor will drop the resistance then that's the only way R1 will ever conduct 1 mA at 18 volts.

 

Theoretical arguments are stimulating. However, I have another project to get to. I'm building a patio this weekend and next. So I must dismiss myself from this conversation for a while. I'll look back this evening and see if I have anything to add (or rebut).

Peace all.

Ciao.

 

So I have two batteries of 9V (so 18V) and a 1MegaOhm resistor.

What I want is a 1 mA current through the resistor.

Even if cooling it resulted in a 56x lowering of the resistance, you would not be getting 1 mA through a 1 MΩ resistor because the resistor would now be 18 kΩ that just happens to have bands on it that indicate that it happens to be 1 MΩ under certain conditions that no longer apply.

The TS was clear, a 1M RESISTOR, not 1M of resistance. He was also clear that he understood the limitations of Ohms Law so he was apparently looking for a "trick" to make it work. I think Tony has provided the best trick so far, cooling. Granted, a temp coefficient that he seeks is unlikely but hey, who knows what happens under 4K.

 

The TS was clear, a 1M RESISTOR, not 1M of resistance. He was also clear that he understood the limitations of Ohms Law so he was apparently looking for a "trick" to make it work. I think Tony has provided the best trick so far, cooling. Granted, a temp coefficient that he seeks is unlikely but hey, who knows what happens under 4K.

By the same reasoning, he could simply re-label an 18K resistor as a 1M with a huge tolerance.

 

By the same reasoning, he could simply label an 18K resistor as a 1M with a huge tolerance.

True.

My point was that WBahn should not be berating @Tonyr1084 for suggesting cooling. There is no solution to the TS's request so, anything is fair game.

 

My point was that WBahn should not be berating @Tonyr1084 for suggesting cooling.

I didn't feel berated over this. I look at all of this as an intellectual argument; the kind Einstein might have with Hawkings. They probably wouldn't agree with each other and each may argue their point of view. I don't equate myself with either Einstein OR Hawkings, but I do enjoy such exercises from time to time. Just like arguing whether time travel is possible. It's thinking outside the box that can produce some unexpected solutions. WOULD cooling the resistor work? I don't know. It's an interesting theory (my opinion). Others see problems with my solution. That's OK. It pushes us all to think in newer and more innovative ways. I doubt I'll ever attempt to test this theory, but in the bane of the question - can one force 1 mA through a 1 meg ohm resistor using just 18 volts - my answer is "I think not. But maybe. Just maybe there might be a way." Anyone who disagrees with me is welcome to do so. ALL are welcomed to do so.

And for those who support my supposition - thanks.

 

Drill a tiny hole end to end then insert a nichrome wire