Actually, the inductance of a straight wire is infinite per unit length, as it has to be integrated out to infinity. It's the return path that limits that infinite inductance.
No...My apologies for not being too clear.
Within a cable which is constrained, coax or wide stripline, the expression for velocity is:
V = 1/sqr(DC), dielectric constant being relative. (edit: many insulations run about 3).
And the relationship between L and C is " LC = 1034 DC.
v = 1/sqr(LC)
For a twin wire, the magnetic field is not confined, so will be higher as a result. This is expressed as:
LC = 1034 EDC, effective dielectric constant...note that this is not indicative of a higher dielectric constant per se, but a way of including the effect of the inductance spilling outside the dielectric.
Also, the velocity relationship still holds slightly modified..
v = 1/sqr (EDC)
this is consistent with:
v = 1/sqr(LC). The E in edc is a simple measure to include the added inductance caused by the wire pair.
This is comparable to the equation:
v = c/sqr(epsilon mu)
j
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Because you had mentioned Ls as part of the tice clock discussion, others discussed the inductance of an extension cord, romex inductance/impedance was being discussed.
I piped up because, as you noted, there were 4 different numbers being bandied about for the exact same entity. I wished to provide accurate information.
j
No, if the wire has greater than zero diameter.
Otherwise it is undefined since natural algorithm of infinity is meaningless.
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Apply a current to a straight piece of wire. Ignore any return path.
Using Ampere's law, calculate the field at a distance R from the wire.
At a distance R, with a known flux, calculate the energy stored in a differential ring around the wire at that radius.
Move out one differential element, and add the energy of that ring.
Repeat to infinity, and you find that the energy is unbounded.
edit: the field is falling as 1/R, but the ring length is proportional to R.
That's why a single wire calculator fails, it doesn't know the return path and must assume something.
j
ps..when I wrote my magfield calculator, I assumed line currents but limited the analysis to a finite distance from the wire, otherwise the fields became too large and inaccurate.. the little black dots are areas of exclusion where the wires are. Red is highest field, blue lower, black zero..
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lossy ac lines
That's a good thing and I understand what you are doing -- I wasnt talking about Ls really - but about tests that correlat with listener comments. Then this 'word' Ls got picked and taken into a direction all its own. I call that a tangent. My input examples to the message I was trying to convey might also be viewed from the roll of Metadata in statistics which get a lot of attention in other places.
Slowly moving forward (i think) -- you can make the line/cord more lossy to conducted RFI by putting selected ferrites on them.
I can offer suggestions. [but first we might have a bunch of tangents to get thru. ;-(]
That's a good thing and I understand what you are doing -- I wasnt talking about Ls really - but about tests that correlat with listener comments. Then this 'word' Ls got picked and taken into a direction all its own. I call that a tangent. My input examples to the message I was trying to convey might also be viewed from the roll of Metadata in statistics which get a lot of attention in other places.
Slowly moving forward (i think) -- you can make the line/cord more lossy to conducted RFI by putting selected ferrites on them.
I can offer suggestions. [but first we might have a bunch of tangents to get thru. ;-(]
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Dick, have you done it again? You mention Ls, but then say it wasn't what you were talking about.
Jn, thanks for the extended explanation, which I need to absorb. I have always considered the electric and magnetic properties of a TEM line to be independent, so I would regard all the magnetic field to be 'outside' the dielectric in the sense that the dielectric is irrelevant to the mag field.
Jn, thanks for the extended explanation, which I need to absorb. I have always considered the electric and magnetic properties of a TEM line to be independent, so I would regard all the magnetic field to be 'outside' the dielectric in the sense that the dielectric is irrelevant to the mag field.
Let me add: and if you can't calculate it properly it does not mean that it is infinity.
Hint: think of a peace of wire of length L and diameter D, as a part of a circle in diameter approaching infinity.
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Ringer alert
Sorry, it seems the extension cord I measured is not some SJ cord. I asked around as to the origins of the cable I was testing since it was substantially different from what was predicted. It seems an Israeli group thought Monster would be interested in selling healthy power cords. Its a sample of a Low EMF (radiated magnetic field) cable sent to us as a sample. Its an interesting patented construction it turns out. The business model did not work so we passed on it. That cable might make for a better speaker cable (also a market that is not big for Monster anymore).
I'll try to find a normal SJ cord to test. At least we are discussing real numbers not speculation.
The question of inductance of a straight wire in free space gets more interesting when you ask how to dump energy into it if it has infinite inductance. . .
Sorry, it seems the extension cord I measured is not some SJ cord. I asked around as to the origins of the cable I was testing since it was substantially different from what was predicted. It seems an Israeli group thought Monster would be interested in selling healthy power cords. Its a sample of a Low EMF (radiated magnetic field) cable sent to us as a sample. Its an interesting patented construction it turns out. The business model did not work so we passed on it. That cable might make for a better speaker cable (also a market that is not big for Monster anymore).
I'll try to find a normal SJ cord to test. At least we are discussing real numbers not speculation.
The question of inductance of a straight wire in free space gets more interesting when you ask how to dump energy into it if it has infinite inductance. . .
No way according to human Calculus. But you can dump an energy into it if it has inductance _approaching_ infinity. The question is valid, when we want to know inductance of it's peace per length.
Edit: let me explain.
Start from the closed loop of a wire of the length L. Then increase loops' length twice, getting inductance of it's half in this loop. And so on. The close the diameter of the loop approaches infinity, the close the loop's part in interest approaches the straight line.
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OK I see. yes I mentioned Ls but within a broader context and didnt mean to have to watch and sit by while pages are devoted to L itself.
And, i am Not saying it isnt interesting. But we tend to loose the original situation. Its kind of like having ADD or adverts interrupting so frequently that a train of thought or the plot gets lost.
But Hey! Its OK. I still have some patience. Thx - RNM
Yes, threads can get like that. I find the time difference can be a problem, as some of the best debates seem to take place once I have gone to bed. By the next morning (in Europe) the conversation may have moved on to something else but many in the US are still in bed. I suppose the same thing can happen, but to a smaller extent, across from East to West Coast over there.RNMarsh said:
I think differential L in wires inside of the house does not matter. What matters, acting of the wire from substation to the house. It is long line, inductance, and antenna for different frequencies, so Zobel on it's end definitely may help.
But as I said many pages ago, the cardinal solution would be, a dynamotor on input to the house, and a Faraday cage around it. Soviet datacenters long time ago used such approach, to avoid information leakage through power lines.
However, modern equivalent would be an isolating UPS, or even DC battery charged from grid, solar panels, and windmill.
But as I said many pages ago, the cardinal solution would be, a dynamotor on input to the house, and a Faraday cage around it. Soviet datacenters long time ago used such approach, to avoid information leakage through power lines.
However, modern equivalent would be an isolating UPS, or even DC battery charged from grid, solar panels, and windmill.
A filter should get rid of most problems, but some people don't like some filters. Why might this be? One possibility is that most mains filters don't absorb noise but reflect it, so the mains wiring can still radiate it into signal wiring. Another possibility is that mains filters affect the detailed shape of the PSU charging pulses and this in turn can affect internal induction between the PSU and signal circuitry. We must always bear in mind that an 'improvement' (e.g. measurable reduction in noise/IM) could sound 'worse' if people have become used to a certain amount of noise/IM and miss it when it is absent.
I can't imagine that. However, some people can associate discotheque sound with heavy clipping, but we here speak about high end quality that people always compare with live music.
Superconducting metal and the rest….
No, no, no . Theories and advanced technologies come and go.
The most impressive of all is the rolling mechanism seen at the lower part of the picture.
George
Fast obvious answer number one: improperly used filters create dirty currents through ground loops.
stole the idea
They stole the idea from the Egyptians. But I think some new civil engineer got credit or points. Seems the Egyptians too used telephone poles to move heavy objects.
And, it took as long -- 2 weeks to move 150 feet to inside the building.
They stole the idea from the Egyptians. But I think some new civil engineer got credit or points. Seems the Egyptians too used telephone poles to move heavy objects. And, it took as long -- 2 weeks to move 150 feet to inside the building.
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The WHY question --> First you have to know that the unwanted signals are either field-coupled or direct-coupled into the wire(s). Thats a technical way to say common-mode or differential-mode and from RFI/EMI or from connected equipment... and characterise it all and quantify it. Then you can just begin to think about making a filter for it. -RNM
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