why not change conventional current to electron current?

[CatalinaWOW]

Your statement:

... and attempt my measurements across those two wires with current flowing.

is vague.

If you are going to measure the potential difference from one and of wire 'A' to the other and the potential difference from one and of wire 'B' to the other, then your experiment is pointless.  The answers can be given using Kirchhoff and Ohm's laws.

What really matters is the voltage across the load.

But your fundamental premise is simply incorrect, so any experimental processes have to be questioned as to how relevant they are in demonstrating the claims.

If there is no clear relevance, then trying to apply some quantitative results is nothing more than useless - unless the intention is to try and bamboozle.  Either way, nothing is proven.

I am not trying to bamboozle or troll anyone.  I would get no pleasure from that, actions like that are juvenile.

The premise of the experiment is that if you use one large conductor and many smaller conductors for multiple devices that are used at the same time, like in an automobile, that the VD would be different on the smaller conductor than on the larger conductor.  And that premise is why that particular power distribution system was decided upon for that application, not to mention that it saves a lot on power wiring.  Again, you need to understand the concept for what you are trying to accomplish. 

I have been nothing but civil and I don't appreciate being called a troll for having a technical conversation about circuit operation.  I have not addressed you in that kind of disrespectful fashion and if you are saying that I am intentionally trying to trick or fool others, you are dead wrong. 

Again, there is a reason that the application in the automobile was designed the way that it was, and you have not provided any other explanation as to why that design was deployed that way.  At this point the voltage across the load is not the concern.  The question is about the distribution of power to multiple devices operating at the same time and what is the most efficient way to provide that distribution.

Rick

I would agree that the choice of current auto manufacturers to make the ground negative is a deliberate choice.  But I don't agree with you about the reason.  A great many early automobiles (and motorcycles) were positive ground.  They worked extremely well.  But having a mixed fleet of positive and negative grounded vehicles is a horrible choice from a maintenance standpoint.  You have to stock more kinds of components, and insufficiently trained repair personnel can make expensive mistakes.  It happens that a market leader used the negative ground approach (and may even have had reasons in mind for doing so, whether they were based on real facts or incorrect understanding) and the market coalesced around that choice.  It would be suicide now to produce an automobile of opposite polarity given how the world has been trained.  And I will also stipulate that there may be corrosion related reasons why that polarity works better, but the reason is not electrical.

[Keyrick]

OK - Lets get something clear.

The whole origin of any 'confrontation' stems from your claim that choosing the polarity of the chassis connection was a deliberate choice, based on good reason - that a negative connected chassis provided tangible benefits over a positive connected one.

Agreed, but not based on "Good Reason" but based on the "Prevailing Thinking" at the time of engineers and physicists.

What others who have challenged this claim (including myself) is that, in practice, it does not matter what polarity is used.  Any circuit under consideration will have the same path - passing through a section of the chassis, the load and a wire - no matter which direction the electrons flow.

No Argument at all.

Do you agree that this is an accurate statement?

Yes it is accurate to the technical point of current flow.  Electron Theory was the prevailing model used at the time.  A decision was made based on this model for certain applications, and it wasn't just a coin toss.  Like I said earlier, in the telecommunications industry the opposite model was/is used, for over a hundred years.  Bell Labs had their reasons as well, and it also wasn't just a coin toss.  This was long before the deployment of semiconductor devices.  You can't base decisions made in the past using the technology of today, because it didn't exist!

I made the statement to provide a reasonable example, based on the Electron Theory that was used at the time, as to why the "Negative Ground" model was chosen.  This is based on my experience in the field.  After college when I started to work in the industry and saw how they did things, (Positive Ground) I was baffled as well, and I asked why.  It was explained to me that the Electron Theory was the settled science, and the decisions were made based on the application at the time.   

IanB, I said that the decision was made base on the ET model.

All, You can look at this issue from both sides and be correct.  To say my explanation is inaccurate without providing alternate reasons for the decisions that were made does not make for a good conversation.  Please tell me your explanation for why these decisions were made.

Rick 

[AndyC_772]

Telecommunications systems use 0V and -48V to protect the integrity of the network from electrolytic corrosion. A buried wire at a positive potential with respect to ground will tend to thin and break, whereas a wire at negative potential won't.

A car has an electrical system which is isolated from earth, so that's not an issue.

None of this has anything to do with voltage drops or power transmission efficiency. The voltages and currents in a system consisting of a battery, load, wires and vehicle chassis, can all be easily calculated just by applying Kirchhoff's laws.

[IanB]

Electron Theory was the prevailing model used at the time.

That really isn't true, especially if "the time" you refer to is the 60's as mentioned in an earlier post of yours.

I think what might have happened is that you went to a technical college and you were given the "simplified" teaching often given to technicians to avoid getting too deep into theory (?).

But it really isn't true that there is or was ever such a thing as Electron Theory. This is just something you have latched onto in your mind. I can assure you that physicists right back to the 1920's and before really knew how electricity worked and would have given you just the same puzzled response we are giving you now if you had brought this up with them at the time.

[IanB]

All, You can look at this issue from both sides and be correct.  To say my explanation is inaccurate without providing alternate reasons for the decisions that were made does not make for a good conversation.  Please tell me your explanation for why these decisions were made.

AndyC has answered you on telecomms.

As far as the polarity of chassis ground on vehicles, this was pretty much a free choice and could have gone either way. Just like driving on the left or driving on the right. Many vehicles were manufactured with positive ground over the years, and the only reason we have negative ground now is because it helps to have a convention that everyone sticks to. It simplifies life for everyone in the industry.

[AndyC_772]

It's probably also worth noting that nothing in Ohm's or Kirchhoff's laws relies on charge being carried by electrons. They're just as applicable if the charge is carried by electrons, holes, ions, or a vast army of really small chimpanzees.

[Keyrick]

Telecommunications systems use 0V and -48V to protect the integrity of the network from electrolytic corrosion. A buried wire at a positive potential with respect to ground will tend to thin and break, whereas a wire at negative potential won't.

Thank you!

A car has an electrical system which is isolated from earth, so that's not an issue.

OK, then why the negative ground convention?

None of this has anything to do with voltage drops or power transmission efficiency. The voltages and currents in a system consisting of a battery, load, wires and vehicle chassis, can all be easily calculated just by applying Kirchhoff's laws.

Kirchoff's voltage and current laws assume the the current transmission medium (wire) is the same and does not take into account different size conductors.  The way the laws apply when using different size conductors is to show the resistance in the individual conductors.

[AndyC_772]

<ducks and hides> 

[miguelvp]

Although there is some truth to that, it is at the lumped element model. But I haven't seen passives with different gauge wires on their ends. Edit: on the same component that is.

And if someone did that because of construction constrains, then they most likely compensate for it.

Edit: for that matter I haven't seen wires that change gauge either other than on analog circuitry but done for specific purposes.

[Keyrick]

Electron Theory was the prevailing model used at the time.

That really isn't true, especially if "the time" you refer to is the 60's as mentioned in an earlier post of yours.

I think what might have happened is that you went to a technical college and you were given the "simplified" teaching often given to technicians to avoid getting too deep into theory (?).

It was a four year school and the curriculum included physics.

But it really isn't true that there is or was ever such a thing as Electron Theory. This is just something you have latched onto in your mind. I can assure you that physicists right back to the 1920's and before really knew how electricity worked and would have given you just the same puzzled response we are giving you now if you had brought this up with them at the time.

I will admit that I have latched on to the ET model.  I won't argue that they didn't know how electricity works, they did, and I believed decisions were made based on that knowledge.

And I thanked Andy for his explanation of the telcom decision to use a -48 volt system.

Regarding Kirchoff's and Ohm's law, a vast army of really small chimpanzees is as good of an explanation as any!

Thanks for the conversation gentlemen.  Decisions were made for reasons.  The sun will rise tomorrow.

Best regards,

Rick

[rs20]

Telecommunications systems use 0V and -48V to protect the integrity of the network from electrolytic corrosion. A buried wire at a positive potential with respect to ground will tend to thin and break, whereas a wire at negative potential won't.

A more "complete" explanation is that by making the buried wires negative with respect to ground, the electrolytic current loops travels from the Telco's grounding stake to the wires, and thus it's the Telco's grounding stake that gets thinned and corroded. Since it's absolutely massive to begin with (compared to the thin underground wires), it'll take decades to deteriorate to a problematic extent. Furthermore, if it does deteriorate, it's easy to find and fix.

A car has an electrical system which is isolated from earth, so that's not an issue.

Well, planet Earth is isolated and that doesn't prevent corrosion from happening in Telco wires on Earth  . If there was a break in a car's wire insulation, connected by rainwater to the body of the car, and then on to the negative terminal of the battery (as is typically done), then the wire will corrode and fail.

Alternatively, if the car's positive terminal was used as a grounding point (equivalently, the car uses -12V with respect to car chassis), then the wire would be fine and it would be the nearby chassis of the car that gets corroded.

So I think this is very much an issue! I'd argue that if I had a break in a wire in my car, I would actually prefer for the wire to rapidly fail so that the problem can be fixed (replacing a wire in a car is ultra-trivial compared to buried telco cable!). A new wire costs much less that a replacement for a rusted-through car chassis!

Whether this was actually a deliberate decision by car-makers though, I have no idea.

None of this has anything to do with voltage drops or power transmission efficiency. The voltages and currents in a system consisting of a battery, load, wires and vehicle chassis, can all be easily calculated just by applying Kirchhoff's laws.

Agreed, of course.

[IanB]

Alternatively, if the car's positive terminal was used as a grounding point (equivalently, the car uses -12V with respect to car chassis), then the wire would be fine and it would be the nearby chassis of the car that gets corroded.

As I mentioned above, many cars (in the UK) were made with positive earth. They lost out to the greater prevalence of negative earth designs.

I'd argue that if I had a break in a wire in my car, I would actually prefer for the wire to rapidly fail so that the problem can be fixed (replacing a wire in a car is ultra-trivial compared to buried telco cable!). A new wire costs much less that a replacement for a rusted-through car chassis!

We could call this the Sony Betamax effect. Technical superiority doesn't always win out.

[vk6zgo]

Electron Theory was the prevailing model used at the time.

That really isn't true, especially if "the time" you refer to is the 60's as mentioned in an earlier post of yours.

I think what might have happened is that you went to a technical college and you were given the "simplified" teaching often given to technicians to avoid getting too deep into theory (?).

A bit "snooty",Ian.

There was indeed something called "Electron Theory"(I remember my Lecturer remarking that it should be called "Electron Fact") at that time,& it was when Techs & others were taught about the makeup of atoms.
This then led into discussion of Electron Flow.---it never had anything to do with Keyrick's assertion.

One could argue that Conventional Current Flow was in fact,the "simplified teaching"

But it really isn't true that there is or was ever such a thing as Electron Theory. This is just something you have latched onto in your mind. I can assure you that physicists right back to the 1920's and before really knew how electricity worked and would have given you just the same puzzled response we are giving you now if you had brought this up with them at the time.

You are spoiling a good argument with an insupportable assertion------Physicists introduced the idea of electrons under just that title.

Where I do agree,is that electrons (or some "pretend" positive charge carriers) do not care if they are flowing from a large conductor into a small one,or the other way round.
It is the total resistance that counts.

Car bodies are used as part of their electrics for no other reason than convenience & savings in copper.
The steel body/chassis has to be there,so why not use it----mild steel isn't as conductive as copper,but the body is huge.

[IanB]

Where it goes wrong is if it leads to some conception that there is a "reservoir" of electrons in a source that flows around a circuit and returns to that reservoir. If this happens it would be better that electrons were never mentioned at all.

[vk6zgo]

Where it goes wrong is if it leads to some conception that there is a "reservoir" of electrons in a source that flows around a circuit and returns to that reservoir. If this happens it would be better that electrons were never mentioned at all.

That is exactly what is implied in Conventional Current Flow,except that it just doesn't identify the charge carriers.

Us lowly Technicians who learnt Electron Flow understood that electrons did not flow end to end at the speed of light,but that there was a more complex interaction taking place.
Nowhere were we told that current gave a damn about the dimensions of part of its path,except as it affects the total resistance.

Keyrick's theory seems to be that the large conductor has many more electrons,therefore current will flow more readily from large to small.
If this was so,such connection would constirute a lossy diode.
The limiting factor is always the size of the small conductor,no matter which way it is connected.
This can be easily measured experimentally.

[CatalinaWOW]

Remember that all the current flow representations are approximations that work well over a wide range of conditions.  As soon as you start talking about time varying voltages or currents the voltages and currents start to leave their homes in the wires, and as dimensional scales approach quantum lengths other rules start to apply.  There are other ways and places that these simple theories stop being enough.

It is always wrong to get too wrapped up in any of our theories as the sole and complete representation of truth.  If one of them works for you, and you are aware of its limitations, go for it.  Everyone has their own mode of learning and what is clear and simple for one is murky for another.  It seems we should all make room for the "easy understanding modes" of others.

[Brumby]

As I mentioned above, many cars (in the UK) were made with positive earth. They lost out to the greater prevalence of negative earth designs.

I would imagine the emerging accessory market would have been a strong influence.

6v systems were around in the early days, too - but I haven't seen that on a modern day vehicle.

[Cerebus]

... Many athletic events are measured in metric units. ...

That's because the rest of us would laugh at you if an American athelete claimed to hold the world record for the "100 yard dash". Just like we do when one of your baseball teams claims to have won the "world" series. 

[CatalinaWOW]

... Many athletic events are measured in metric units. ...

That's because the rest of us would laugh at you if an American athelete claimed to hold the world record for the "100 yard dash". Just like we do when one of your baseball teams claims to have won the "world" series. 

Its sillier than you imagine.  The "official" world record for the 100 yard dash is held by a Jamaican.  Who was running a 100 meter race.  But somehow they figured the time it took him to cross the 100 yard line and it is now the "official"  record.  It has been a long time since 100 yard races have been run in international events, and quite a while since they have been held here in the US.  The most recent records for a 100 yard race are 40+ years old.

As for the World Series, it is a little pretentious now, but they got their name back when there really wasn't anybody else playing baseball.  I guess we should apologize for the fact that the sport has become popular in many parts of the world.  If it makes you feel any better, the Little League version of the World Series is now actually an international event, although I am sure someone somewhere feels left out.  US teams still win sometimes as do teams from other American countries, but it seems that the best youth baseball is generally played on the west side of the Pacific Ocean.