Jan,
Should we talk about SWR?
There is a really cute experiment you can do. Get a 1-2 M length of copper pipe. Pass one conductor of your loudspeaker cable through it. Also pass through it two snall gauge pieces of insulated wire. Terminate one end of each smaller wire at opposite ends of the tubing. The open ends of each wire go to a 100 ohm resistor which then is connected to the tubing. Measure the voltage across each resistor while playing music. You will be able to not only see the direction of power but also the mismatch.
Should we talk about SWR?
There is a really cute experiment you can do. Get a 1-2 M length of copper pipe. Pass one conductor of your loudspeaker cable through it. Also pass through it two snall gauge pieces of insulated wire. Terminate one end of each smaller wire at opposite ends of the tubing. The open ends of each wire go to a 100 ohm resistor which then is connected to the tubing. Measure the voltage across each resistor while playing music. You will be able to not only see the direction of power but also the mismatch.
Last edited:
You will see more voltage across the resistor on the loudspeaker side. It is a simple method to show forward and reverse power.
Enough people have responded since to correct this false claim. Do you still hold to it? You do understand that power does not move along transmission lines, but current (which is entirely AC)? A resistor exhibits no difference in operation if power flow changes direction, since all the resistor 'sees' is AC current.
Neither voltage nor current is directional, the directionality convention of power is derived by comparing the phase angle between the polarizing quantity (voltage) and the operating quantity (current). Convention defines, based on this phase angle difference, when the power is positive and when it is negative (which was aligned with the understanding that positive power is consumed by a resistor, and generated by a generator). VAr convention is embedded in this too, but pointless to go into.
Important point for this discussion is that the quantities involved are completely non-directional. Waveform asymmetry is easily addressed through harmonic analysis, which deals with (drum roll) symmetrical and 100% non-directional quantities. Even harmonics, although rare in power systems, are still symmetrical and non-directional by superposition.
obviously you are the one and only who did this experiment.
It could be interesting to learn the voltages you measured there, i.e. numbers you read at your instruments.
I have no clue where you get your conventions. Current is usually considered to flow from positive to negative in normal convention. In fact it really flows the other way.
In power convention devices which source power are considered to have a positive value of power flow and devices which consume power a negative value.
Power Factor is of course determined by the phase angle between voltage and current.
As to power distribution distortion typical values these days reach 5% THD at the user. Most folks can use a simple oscilloscope to observe this, but there are instruments that will actually do a FFT of the power line and show the harmonics, such as my Tektronix THS720P.
As to symmetrical analysis you just might be shocked to find out that using a discriminator detector with a transformer you can measure asymmetry on many power lines. Attached is a sample circuit. Plug it in one way and it may read a positive value, reverse the AC line connection and the value switches polarity.
As to the original poster was asking if others have noted directionality to the specific resistors, many responded with their opinions. The only other observed response interestingly confirmed the original question. So I actually did a measurement. One that I will repeat a few times with variation of some of the parameters.
As you seem to be unaware the resistor type in question does change distortion with frequency more so than other types.
Attachments
You can measure SWR down to some low frequencies if your bridge coupling is long enough. But I wouldn't try that technique at power line frequencies.
One of the "Cold War" inventions was a clamp on telephone line tap that could pick out individual wire pairs' signals in a multipair cable. Think 50-200 twisted pairs and listening to each conversation by itself!
Are you saying power direction has no relation to the angle between voltage and current, but power factor does?
https://www.msl.irl.cri.nz/sites/all/files/training-manuals/TG28 Mar 2013.pdf
This is just industry wide standard convention.
NO. Normally the difference is adjusted to be small to maximize efficiency in loads or generation. Until Solar power became common users were loads only! In many places the energy delivered is charged at a different rate than that returned. Some places by law it must be equal and utilities don't like to buy power at retail.
We are obviously getting nowhere in this discussion. You said power factor is determined by the angle between voltage and current, but were also implying that power direction (or polarity) is not. I am saying the angle determines not just power factor, but also power polarity (positive or negative). It is industry convention that defines this.
In Post #211 you took exception to cbdb's comment that AC has no direction, based on a power plant providing power to users in a 'direction'. Then asking if resistors behave differently if power flows in one direction versus another.
The error you make is assuming power flows in 'direction' - it is simply a convention to make the maths work. All the resistor sees is a nondirectional, AC current - there IS NO DIRECTION.
Nothing to do with electron flow vs conventional current flow.
Absolutely no idea what you are trying to say in Post 230. Post 229 was a futile attempt to teach you something, which based on the time it took you to repost you clearly did not read. Power factor is also completely irrelevant to this discussion, so why bother bringing it up? The issue is directionality of a passive resistor, and a recent addition of the directionality of power flow. I am trying to correct your misconceptions of the latter.
In Post #211 you took exception to cbdb's comment that AC has no direction, based on a power plant providing power to users in a 'direction'. Then asking if resistors behave differently if power flows in one direction versus another.
The error you make is assuming power flows in 'direction' - it is simply a convention to make the maths work. All the resistor sees is a nondirectional, AC current - there IS NO DIRECTION.
Nothing to do with electron flow vs conventional current flow.
Absolutely no idea what you are trying to say in Post 230. Post 229 was a futile attempt to teach you something, which based on the time it took you to repost you clearly did not read. Power factor is also completely irrelevant to this discussion, so why bother bringing it up? The issue is directionality of a passive resistor, and a recent addition of the directionality of power flow. I am trying to correct your misconceptions of the latter.
This funny little organization called IEEE.
https://www.google.com/imgres?imgur...ved=0ahUKEwjm2Kiz0MTRAhUCSSYKHW4ABJgQ9QEIIDAA
If there is a difference that depends on which way the resistor is hooked up, then it isn't a resistor. That should be a cause for concern. In an AC circuit (audio is AC) that would mean that there would be hysteresis in normal operation. That means the circuit in which the resistor is placed behaves differently on the positive swing of the audio signal than on the negative swing, which introduces distortion. Unless I am missing something.
What you quote here is consistent with the concept of power flow. It nicely shows the USA convention vs what used to be the DIN version, now the IEC.
Like slowing down to look at an accident.
Actually I think we try to stop the spread of this nonsense.
..from your point of view and that of others, but not all.
The fact this thread was created and a few people are interested in the OP's point of view, makes your claim sound out of place a bit.
I'm working on it. It won't be ready for tomorrow.
Nice post. I might add "there's no proof of Rs electrical directionality, but maybe something else makes them have one. Just an abstract hypothesis.
He primarily asked for advice related to his audio methodology that he didn't receive from most folks here in a content of 24 pages. Does he need an evidence?
Is it against the rules of this forum?
