a question about resistors in an arc experiment

Regardless of what the circuit simluation does, I won't know what point he thinks he's making unless he tells me.

Sylvia.

If you think it's a bad photo to judge from, then why are you judging from it?

Sylvia.

On Sun, 18 Jan 2009 12:33:10 -0800, John Larkin wrote:

--- No, it doesn't.

Here's my circuit alongside an identical generator with an ordinary 1k resistor to ground. Probe them and see if they act the same:

Version 4 SHEET 1 880 680 WIRE 176 -32 128 -32 WIRE 320 -32 256 -32 WIRE 192 80 -16 80 WIRE 192 128 192 80 WIRE -512 144 -672 144 WIRE -16 144 -16 80 WIRE -16 144 -288 144 WIRE 0 144 -16 144 WIRE 128 144 128 -32 WIRE 128 144 80 144 WIRE 160 144 128 144 WIRE 320 160 320 -32 WIRE 320 160 224 160 WIRE 160 176 128 176 WIRE 192 208 192 192 WIRE 192 208 16 208 WIRE -672 240 -672 144 WIRE -512 240 -512 144 WIRE -288 240 -288 144 WIRE 128 256 128 176 WIRE 176 256 128 256 WIRE 320 256 320 160 WIRE 320 256 256 256 WIRE 128 304 128 256 WIRE -672 416 -672 320 WIRE -512 416 -512 320 WIRE -512 416 -672 416 WIRE -288 416 -288 320 WIRE -288 416 -512 416 WIRE 16 416 16 208 WIRE 16 416 -288 416 WIRE 128 416 128 384 WIRE 128 416 16 416 WIRE 128 464 128 416 FLAG 128 464 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 -48 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 490 SYMBOL voltage -288 224 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 12 0 .01) SYMATTR InstName V3 SYMBOL res 96 128 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R4 SYMATTR Value 490 SYMBOL Opamps\\\\LT1797 192 96 R0 SYMATTR InstName U1 SYMBOL voltage -672 224 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 12 0 .01) SYMATTR InstName V1 SYMBOL res -528 224 R0 SYMATTR InstName R5 SYMATTR Value 1000 TEXT -8 440 Left 0 !.tran .02 uic

---

--- But it's _not_ stuck at ground, it ramps up to about 190mV during the time the output from V3 is ramping up to 12V.

JF

--
I don\'t think he has one of her in her nudist days.

JF

There is not, and never was, any dispute about the possibility of a negative resistance characteristic. Nor is there, nor ever was, a dispute about the possibility of constructing something that exhibits behaviour, over a limited range, that replicates some of the behaviour that a negative resistor would have.

The issues, as I remember them, were firstly, whether an arc had negative resistance, as distinct from having a resistance characteristic that, over part of its range, leads to current dropping with rising voltage, and secondly, whether a circuit containing a power source could legitimately be called a real negative resistor.

Your circuit simulation doesn't advance matters at all.

Sylvia.

--- I've already told you what the point was, but you don't seem to get it. So, run the simulation and if you still don't get it I'll explain it to you in greater detail and in simpler terms.

Here's the latest:

Version 4 SHEET 1 880 680 WIRE 400 -112 -96 -112 WIRE 176 -32 128 -32 WIRE 320 -32 256 -32 WIRE 192 80 -16 80 WIRE -96 112 -96 -112 WIRE 192 128 192 80 WIRE -16 144 -16 80 WIRE -16 144 -288 144 WIRE 0 144 -16 144 WIRE 128 144 128 -32 WIRE 128 144 80 144 WIRE 160 144 128 144 WIRE 320 160 320 -32 WIRE 320 160 224 160 WIRE 160 176 128 176 WIRE 192 208 192 192 WIRE 192 208 16 208 WIRE -288 240 -288 144 WIRE 128 256 128 176 WIRE 176 256 128 256 WIRE 320 256 320 160 WIRE 320 256 256 256 WIRE 128 304 128 256 WIRE -96 384 -96 176 WIRE -288 416 -288 320 WIRE 16 416 16 208 WIRE 16 416 -288 416 WIRE 128 416 128 384 WIRE 128 416 16 416 WIRE 128 464 128 416 WIRE -96 528 -96 448 WIRE 400 528 400 -112 WIRE 400 528 -96 528 FLAG 128 464 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 -48 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 490 SYMBOL voltage -288 224 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 12 0 0 .1) SYMATTR InstName V3 SYMBOL res 96 128 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R4 SYMATTR Value 490 SYMBOL Opamps\\\\LT1797 192 96 R0 SYMATTR InstName U1 TEXT -8 440 Left 0 !.tran .02 uic TEXT -112 416 Left 0 ;> >

TEXT -112 144 Left 0 ;> >

JF

--
Since my circuit is of the \'secondly\' genre, then the only issue which
seems to be at hand is whether its power supply precludes it from being
legitimately called a negative resistance device/negative resistor.

If you\'ve run the simulation, the issue should have been resolved.

Have you?


JF

No. It hs a power supply.

Explain why you think this wouldn't exclude it from being called a negative resistor.

Sylvia.

Well, of course it goes up a tiny bit as the current through the divider increases. It's locked up and saturated, but it's not a

*perfect* ground. But the important thing is that the direction that the opamp output is going is slightly UP, as you noted, in the SAME direction as the input, so all it's doing is adding a little more ordinary, POSITIVE resistance in series with the 1K.

You could replace the opamp with roughly a 16 ohm resistor to ground and get the same waveforms. Try it. How can three resistors in series be a negative resistor?

How could a tiny voltage change at the bottom of R3, in the POSITIVE direction, swing the whole R4+R3 impedance negative?

This is just too silly.

John

No problem. I'm just an ordinary hairy-as-an-ape kind-a-guy ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
 I love to cook with wine     Sometimes I even put it in the food

--
Run the simulation first and if you don\'t get it I\'ll tell you.

JF

There is a tendency for the "boys" here to gang up on and try to chase women away; it's happened several times before.

I'll certainly debate you about circuit theory, or even programming, but I can't imagine why these guys feel so threatened that they have to act the way they are doing now.

It all mystifies me.

And, for the record, I *like* most all women. I am attracted to the thinner ones, which is just chemistry.

Oh, I was describing my ideal, verbose, safe, boring programming language to a guy last week, and he said "Oh, that's ADA." He also said that VHDL is based on ADA, which may explain why hardware is so good and most software (C, C++) is so bad.

I've got to read up on ADA. Most of the stuff that runs airplanes is coded in ADA.

Grumble, snarl, back to my program, up to 5762 lines of assembly so far.

John

--
Well, then, the simulator must be wrong.

JF

Can't be bothered. If you have a point to make, then make it. Otherwise shut up about it.

Sylvia.

--
Coming Into Los Angeles
Words and Music by Arlo Guthrie
.
.
.

Hip woman walking on a moving floor
Tripping on the escalator
There\'s a man in the line
And she\'s blowing his mind
Thinking that he\'s already made her
.
.
.

;)

JF

Just trying to give you a hard time... this is, after all, your initiation period ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
 I love to cook with wine     Sometimes I even put it in the food

[snip]

And YOU have advanced our knowledge how?

(Not at all, actually. We're just feeding you rope from which to hang yourself ;-)

An arc _does_ have a negative resistance _region_.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
 I love to cook with wine     Sometimes I even put it in the food

Yup, if LT Spice is broken we both save face.

There's a more fundamental way to look at this circuit. Treat the source V3 as a battery. If V3 is 12 volts, and the circuit indeed pushes 12 mA *into* V3, then the battery is being charged. That makes sense: a real resistor discharges a battery but a negative resistor charges it.

So this circuit, one LTC opamp and four resistors, is delivering power into V3. It's a perpetual motion machine.

John

Yes. Thankyou. That was never in dispute.

Sylvia.