a question about resistors in an arc experiment

Really? What's wrong with it?

--

John Devereux

--
Nope.  Can\'t find it on Youtube either. :-(

JF

It's incomplete. It has no power supply.

Which is significant. You cannot simulate a negative resistance without a power supply, because it is an energy source. The fact that it needs a power supply emphasises the fact that it only simulates a component with negative resistance. It isn't a real negative resistor. The highly desirable real negative resistor, were one to exist, would function indefinitely. A simulation can only function as long its energy reservoir lasts.

Sylvia.

[...]

Hi Silvia,

You can use a battery.

Of course, the energy comes from the supply.

But it is nevertheless a negative resistor / resistance during that time IMO. Put it in a box with a bettery and bring out the input terminal and GND. It's a negative resistor - i.e. a two terminal circuit with negative resistance. It will have limits of operation determined by the components used (but so does a "real" one).

--

John Devereux

In article , snipped-for-privacy@InfiniteSeries.Org says...>

Your logic is AlwaysFlawed, Always Wrong. All it means is that JG is wrong, in this case.

Dim logic, DimBulb.

There are none as blind as a DimBulb.

I can.

In article , snipped-for-privacy@InfiniteSeries.Org says...>

AlwaysWrong is, surprise, wrong again.

--
Like this one?:

Version 4
SHEET 1 880 680
WIRE 176 48 128 48
WIRE 320 48 256 48
WIRE 192 96 -176 96
WIRE 192 128 192 96
WIRE -176 144 -176 96
WIRE -32 144 -176 144
WIRE 128 144 128 48
WIRE 128 144 48 144
WIRE 160 144 128 144
WIRE 320 160 320 48
WIRE 320 160 224 160
WIRE 160 176 128 176
WIRE 192 208 192 192
WIRE 192 208 16 208
WIRE 128 256 128 176
WIRE 176 256 128 256
WIRE 320 256 320 160
WIRE 320 256 256 256
WIRE -176 288 -176 144
WIRE 128 304 128 256
WIRE -176 416 -176 368
WIRE 16 416 16 208
WIRE 16 416 -176 416
WIRE 128 416 128 384
WIRE 128 416 16 416
WIRE -176 464 -176 416
FLAG -176 464 0
SYMBOL res 112 288 R0
SYMATTR InstName R1
SYMATTR Value 100k
SYMBOL res 272 240 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 100k
SYMBOL res 272 32 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R3
SYMATTR Value 1k
SYMBOL voltage -176 272 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value PULSE(12 0 0 0 .1)
SYMBOL res 64 128 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 1k
SYMBOL Opamps\\\\LT1211 192 96 R0
SYMATTR InstName U2
TEXT -160 440 Left 0 !.tran .02 uic

JF

You're a retard. You "cannot".

:) You need a supply, of course.

Perhaps I can sell them on ebay to free energy nuts - a solar powered negative resistor perhaps!

[...]

Version 4 SHEET 1 880 680 WIRE 192 48 160 48 WIRE 304 48 272 48 WIRE 160 128 160 48 WIRE 160 128 -64 128 WIRE 192 128 160 128 WIRE 304 144 304 48 WIRE 304 144 256 144 WIRE 160 160 112 160 WIRE 192 160 160 160 WIRE -64 176 -64 128 WIRE 112 208 112 160 WIRE 160 208 160 160 WIRE 192 208 160 208 WIRE 304 208 304 144 WIRE 304 208 272 208 WIRE 112 304 112 288 FLAG 112 304 0 FLAG -64 256 0 SYMBOL Opamps\\\\opamp 224 80 R0 SYMATTR InstName U1 SYMBOL res 96 192 R0 SYMATTR InstName R1 SYMATTR Value 1 SYMBOL res 288 192 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R2 SYMATTR Value 1 SYMBOL res 288 32 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 1 SYMBOL voltage -64 160 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 1 TEXT 192 296 Left 0 !.lib opamp.sub TEXT 144 408 Left 0 !.tran 1

--

John Devereux

slope

--
It\'s got one: V3, which is also the current-controlling input to the
negative resistance, which satisfies Sylvia\'s criterion for a real
negative resistor.

That is, looking at the circuit like a black box with two terminals,
when the voltage across the terminals falls, the current through them
will rise and the circuit will function indefinitely.

JF

[...]

Heh!

I don't know if attachments work in XNews. Have to try it and see how it comes out.

Anyway, here's your neat circuit with a sine wave input and a resistor R1 in series. Play with the resistor.

Regards,

Mike

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[...]

Hmm, that circuit behaves strangely on my LTSpice (with the current from V3 rising to 27KA)!

--

John Devereux

Pity; arcs can be interesting.

I have a nice explanation of arc negative-resistance behavior in my copy of Morecroft's great "Principles of Radio Communication", 2nd edition, 1927. I could post it if anyone were seriously interested. Negative-resistance Poulson arc transmitters were being built up to the megawatt level.

ftp://jjlarkin.lmi.net/Poulsen.JPG

A Poulsen arc transmitter in Pearl Harbor was the only reliable means of communicating to US submarines during WWII.

I'm sure that MiniProng has no interest in things like this.

John

--
I think something in the model goes bonkers when the supply voltage goes
below a certain limit.

Try an LT1007; it works pretty good.

JF

--
Better yet, try some of the rail-to-rail input and output devices.
LT1797 looks near perfect.

JF

I think the problem with that one is the current-voltage line does not go through the origin. (In fact the simulation is still unphysical for me, with current at -8mA at 0V supply!)

For me, the essential quality of a "resistor" would be that it should closely follow Ohms law. That is, I = V/R where R is a constant (or close to it).

--

John Devereux

I have the movie on DVD...

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
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 I love to cook with wine     Sometimes I even put it in the food

You sound like a leftie weenie, telling me what *I* can believe, DimBulb.

When we (engineers who design electronics) draw opamps, we don't always show the power supplies, because we all know that opamps need power supplies to work. And we don't always insert every adjective and every qualifier into a sentence where we know other circuit designers will perfectly understand our intent. And most of us take conservation of energy for granted.

In other words, don't be a PITA.

Good grief.

John