a question about resistors in an arc experiment

S Claus · 2009-01-15T03:40:28+00:00

Hi allI was browsing through the book "Analog Circuit Design: Art, Scienceand Personalities" and checked on Chapter 8, titled "True AnalogCircuit Design". On page 59 in this chapter, Tom Hornak writes abouthow he got involved in electronics when he was younger. He explainshis and his friends first hands-on experiment which dealth withelectric arcs as thus:We used a 1kW smoothing iron as a series resistor and large iron nailsas electrodes.I had a dumb question about this, which is that what is the reason forusing a resistor in this type of experiement? I mean, would there notbe more current and therefore a larger arc if no resistor was used?How is the limiting of the current flow (by the resistor) desireable?

J

Jim Thompson 17 years ago

Scrawny broads shouldn't join nudist groups ;-)

Neeerp! Not enough "active area" ;-)

...Jim Thompson

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J

Jim Thompson 17 years ago

Sure you do (any Spice program). You just don't know how to do it, Scrawny Sylvia ;-)

...Jim Thompson

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John Larkin 17 years ago

Get LT Spice. It's free.

John

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MooseFET 17 years ago

e

ts

of

I have considered the case. It depends on whether the negative resistance is greater than infinite or less than zero. Unlike positive resistance, there are two types of negative resistance.

That is not correct for this circuit:

----/\\/\\--- ! ! -+--!-\\ ! ! >-----+ -!+/ ! ! ! +---/\\/\\--- ! \\ / \\ ! GND

This circuit is stable with a high impedance input.

Actually yes it is. It follows exactly Ohms law and has a minus sign in it.

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J

John Larkin 17 years ago

I like skinny women. You can have the tubbies.

John

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Sylvia Else 17 years ago

It's not clear to me what it means to say that a resistor has a resistance that is greater than infinite. What is the defined behaviour of such a resistor.

Yes. Which means it's not a correct emulation of a negative resistor, because the latter is not stable with a high impedance source.

It has a characteristic of which Ohms law is a solution, but different stability from a real negative resistor.

Sylvia.

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Sylvia Else 17 years ago

You've just added in a simulation of an infinitely long lasting power supply.

Making a real negative resistor along those lines would involve having a real infinitely long lasting power supply. Last time I checked, they were hard to come by.

Sylvia.

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Archimedes' Lever 17 years ago

Positively excellent retort.

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StickThatInYourPipeAndSmokeIt 17 years ago

And to think that you fat, retarded bastards have been calling me a troll.

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StickThatInYourPipeAndSmokeIt 17 years ago

I would say zero current flow. As in open circuit.

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Sylvia Else 17 years ago

Certainly the current tends towards zero as the resistance tends towards infinity (or minus infinity).

But for a resistance that is "greater than infinite"? Not possible to say without a definition of the term.

Sylvia.

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J

JosephKK 17 years ago

Interestingly prissy pants for someone who chooses to live and work in San Francisco.

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JosephKK 17 years ago

I remember TV, then i found USENET. Infinitely more entertaining.

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JosephKK 17 years ago

power.

Stress is largely something you do to yourself.

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John Fields 17 years ago

Have you managed to run my simulation yet? JF

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John Fields 17 years ago

slope

You\'re looking at the wrong thing. Look at the voltage into R4 and the current through it. With a rail-to-rail input and output opamp it\'s much nicer: Version 4 SHEET 1 880 680 WIRE 384 -16 -96 -16 WIRE 176 48 128 48 WIRE 320 48 256 48 WIRE 192 96 -32 96 WIRE -96 128 -96 -16 WIRE 192 128 192 96 WIRE -32 144 -32 96 WIRE -32 144 -288 144 WIRE 0 144 -32 144 WIRE 128 144 128 48 WIRE 128 144 80 144 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 -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 -96 400 -96 160 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 -96 512 -96 432 WIRE 384 512 384 -16 WIRE 384 512 -96 512 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 32 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(12 0 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

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Sylvia Else 17 years ago

I haven't tried. I don't see what point you think you're making.

Sylvia.

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John Fields 17 years ago

No, I\'ve just made the input signal the opamp\'s power supply as well, obviating the need for an infinitely long lasting power supply. After all, if there\'s no signal present of what use is the supply?

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John Fields 17 years ago

You\'ll never know if you don\'t try... Anyway, What\'s the matter; afraid you might learn something and feel indebted? JF

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Fred Abse 17 years ago

Not as much fun, though ;-)

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)

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a question about resistors in an arc experiment

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