Different sinewaves to each end of single wire

What happens when you feed a sinewave into each end of a length of straight wire, but the sinewaves differ in frequency. Amplitudes are the same. There is no connected ground reference.

Is there an internal current flow between the higher and lower frequency ends of the wire? If so, how can it calculated or measured?

Kevin Summers

Reply to
ksummers
Loading thread data ...

A sinewave is a mathematical construct.

Use of the word "amplitude" suggests you're feeding a voltage into each end. For wire of zero resistance and short relative to the wavelengths involved, you can't do that. And you need a common reference, normally called ground, but can be any point.

If you feed current, superposition applies. Actually, superposition applies if you try to feed voltage, but you have to measure it fast before the smoke gets out. ;-)

Reply to
mike

Your question seems rather ill-defined.

You say "feed a sinewave into each end of a length of straignt wire", but you aren't saying what the sinewave (presumably a voltage) is with respect to. You specifically say "there is no connected ground reference". So, you seem to be trying to push a signal into a straight wire out of one output terminal on the pushing device, without having anything connected to the other terminal (or ground shell) of that same device.

You aren't saying whether the wavelengths of the signals are longer than, similar to, or much shorter than the length of the wire. You aren't saying whether there's any form of radial or counterpoise attached to one or the other generator (or both). You aren't saying whether you care about energy radiated into space.

If this is a homework question, the Magic 8 ball says "Answer hazy, ask again later."

--
Dave Platt                                    AE6EO 
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior 
 Click to see the full signature
Reply to
Dave Platt

Nothing happens, both sources (assuming voltage sources) flapping in the wind.

Tim

--
Deep Friar: a very philosophical monk. 
Website: http://seventransistorlabs.com
Reply to
Tim Williams

There is no current because both sources are commonly isolated.

It would be the same as if you were to put the + & - together on two cells but didn't connect the other ends. Cells being, two different sources of energy..

Reply to
Jamie

More like farting in the wind!

Jamie

Reply to
Jamie

Judging by the responses so far, my question was not explained well enough.

To be more specific. Two AF sinewaves, being of dissimilar frequency and identical amplitude, would be applied one each to the ends of the same wire air coil, via channel A and B of a single ended, stereo amp. A resistor would be placed in series on each side for loading.

While there is admittedly no "return" for each sinewave, they originate from the same device, the internal circuitry of which has a common ground.

The question is, what happens in the coil (wire)? I would expect the two sinewaves to "fight" each other, with the higher frequency side (greater signal density) transferring current toward the lower.

Also, how would this affect the amp?

Kevin Summers

Reply to
ksummers

That most definitely defines a return path.

There is only one current. It's the instantaneous difference in the voltages at each end divided by the total impedance.

If the amp is designed to put 8V into 8 ohms, it can source an amp. If you put out of phase signals and try to get 16V into 8 ohms or 2 amps. That is probably considered an overload. If you halve the amplitude or double the resistance, you're back to an amp.

Where is this discussion going? What are you trying to accomplish?

Reply to
mike

Don't they teach trigonometric identities at school any more? Hint:

sin(A) + sin(B) = 2*sin((A+B)/2)*sin((A-B)/2)

The full treatment of this includes dissimilar amplitudes and is not that much more complicated.

Let A = ut, B= vt and do the sums yourself

--
Regards, 
Martin Brown
Reply to
Martin Brown

OK

So, if I understand correctly, the conducted current would fluctuate at the "beat" frequency between the input sinewaves.

For example, if channel "A" is feeding in 100Hz, and channel "B" is

200Hz, the current fluctuation occurs at 100Hz. This would appear to nullify the 200Hz component of the current.

Does this concept have potential applications, or am I dreaming?

Chris Warren

Reply to
cwarren

Noise canceling headphones.

Reply to
DecadentLinuxUserNumeroUno

There has to be a complete circuit, but a 2 wire to 4 wire hybrid is part of any duplex phone line, the process is called duplexing.

Reply to
dave

You're overthinking it. Do the math. Write the equation and try find values for amplitudes VA and VB that cancel B. I think the only solution is where the amplitude of VB is zero. It is what it is. Generalizing dosen't change the math.

If you're asking if the concept of superposition has applications, yes it's everywhere. If you're asking if you can use 100Hz. to cancel 200Hz., with pure sinewaves in a linear system, no.

Reply to
mike

Yes, there is. The internal impedance to ground of each source.

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
 Click to see the full signature
Reply to
Fred Abse

OK, two final questions please. Excuse me for avoiding the math experience.

  1. I didn't mean to imply VB was zeroed. Rather, is it in any way _reduced_ by the situation I described?

  1. Is my assumption correct about current flowing from the high frequency side (VB) toward the low frequency side (VA)? Is this then proportional to the ratio between the two frequencies?

Since you already seem to know, your considered reply would be appreciated.

Thank you for your patience.

Chris Warren

Reply to
cwarren

No (not if it's a perfect voltage source; typically, an audio amp makes a reasonable approximation, given a known load resistance anyway, which has now been defined).

He was saying, the only condition under which that even could be true is the trivial case, i.e., where it's zero anyway.

Only for some instants in time. Current also flows back when VB(t) > VA(t).

No, the current alternates constantly between positive and negative, according to the superposition of currents.

Tim

--
Deep Friar: a very philosophical monk. 
Website: http://seventransistorlabs.com
Reply to
Tim Williams

No, you're not excused from avoiding the math. It's very simple and explains the system. You gotta learn to do math, even if it's approximations in your head, to understand.

There is no high frequency side. For the purposes of this discussion, you have one wire that you're poking electrons at.

Think about the "executive toy" with four balls suspended from V-strings. Think of the balls as electrons. You pull out the ball on one end and let it go. If you put an electron in one end, it knocks another out the other end. Since it's AC, the process is symmetrical and the electrons just slide back and forth with the direction determined by the instantaneous value of the current.

Short answer, no. If you can reduce it, you can reduce it to zero...assuming you don't have other constraints to satisfy.

At the macro level, no, and no. The instantaneous current flow is from the higher instantaneous voltage to the lower voltage. Sinewaves have an average level of zero, so the current flows either direction and the electrons rattle back and forth generating heat, but the average electron flow is zero.

Several here have replied. Problem is that your fundamental understanding of what's happening is flawed. You want someone to just say, "yes", but it ain't so.

Would I be correct in saying that apples are easy to harvest because they float? NO, they're not easy to harvest, but it's not because they float. And the discussion is going nowhere until you can grasp the concepts of a tree and a ladder.

You seem unwilling to disclose the problem you're trying to solve. That is not patience-inducing. You're not gonna learn basic electronic concepts here. Best that can happen is that you get help solving a particular problem.

If you think you've discovered something novel, statistics are against you. Most "inventions" are merely the result of misunderstanding.

Reply to
mike

At least one responder stated that the amp's performance would be affected by the wiring I describe, which was my impression. How can this be if the net effect is supposed to be zero?

Aren't we confusing work-done with what is happening in real time? The instantaneous current changes within the wire/coil are precisely what I am interested in.

If I drive my car back and forth in the same spot, I go nowhere. That does not mean nothing is happening.

For example, could you say the coil is not radiating an EMF as a result of the two dissimilar sinewaves applied?

If not, then why, if there are in fact instantaneous current changes?

Chris Warren

Reply to
cwarren

The issue with this level of math is that there is an assumed time-frame and end result, like a snapshot.

Are you really saying that nothing tangible is happening? Isn't the coil is an emitter of EMF due to the current reversals?

Yes, but as another respondent pointed out, it does occurs on an instantaneous level. Additionally, if the net work is zero, why does the amp see a load?

There is no "problem". I just wanted to understand what happens in the situation described.

If my original inquiry is evolving in response to input here, then I would see this as a success. Patience is a virtue.

Chris Warren

Reply to
cwarren

And math is your mother >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
 Click to see the full signature
Reply to
Jim Thompson

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.