why not change conventional current to electron current?

[d4n13l]

I'm just wondering why the world didn't change what is know to be as the conventional current to the actual electron current when it was confirmed that it was electrons that moved? or why hasn't it happen since then? I know that in practical terms is the same, but this is just the source of so much confusion.

In the past maybe it was hard to connect with everyone and agree on a new convention, but new generations are aware about the right way current flows, so why not stick with it?

[IanB]

I'm just wondering why the world didn't change

this is just the source of so much confusion

When you are confused about something it is not the world that has to change, it is you that has to change. You need to work on not being confused.

[Brumby]

+1

Don't fret about it.  Just go along with the convention and you can live a normal and happy life being productive in just about any field.

IF and I mean IF you ever get into a profession where you do actually need to know the difference, then worry about it.

[HAL-42b]

Why doesn't US finally switch to the Metric System? Why doesn't the world switch to DC power grid? Why are we still driving combustion cars? Why don't we abandon the stupid Philips screws for Torx?

You see, asking why other people won't do X or won't do Y is fruitless.


Besides, if we solved all the problems there wouldn't be any more problems for the next generation to solve. 

[Muxr]

Why don't we abandon the stupid Philips screws for Torx?

Haven't thought of that one, that would be neat.

[Rerouter]

Here is a question, how many people have you met that pretty much accept technology as magic? As a black box to never be opened?,

Now think about how many people are raised on the water analogy, they can imagine one side being at pressure because its full of something (Positive Charge), Than they can the other side being at near vacuum (Negative Charge), Its these small differences that make one approach more easily taken up,

Equally, how many Electricians, or even Electronics Enthusiasts care about which direction electrons flow across a junction of materials, not many, its only the minority that it concerns, and they understand well enough to treat both,

[rs20]

The more pragmatic question is; why do people even tell students about electron current in ELECTENG 101? I was fortunate enough to learn electronics with a Dick Smith Electronics kit when I was young; when I went to university I knew to ignore the silly man talking about electrons.

Don't get me wrong, it becomes important in year 3 when talking about the theory of operation of MOSFETs and so on; I just don't get why it's mentioned so soon. It's not like there's any obvious contradictions anymore, like the current flowing from the cold side to the hot side of a vacuum tube.

[Mechatrommer]

I'm just wondering why the world didn't change what is know to be as the conventional current to the actual electron current when it was confirmed that it was electrons that moved?

because someone or somebunch fucked up with the convention in the beginning and now it is accepted everywhere from the highest theorists in universities, to the lowest practicalists in the backyards. trying to change the whole ecosystem is close to impossible now.. similar to left vs right driving countries is the source of confusion if left side drivers go to the right side driver country. but in order to change the system, a country or the government will be close to being fucked up, esp large country like america...

[rs20]

Why doesn't US finally switch to the Metric System?

This raises a good point as well -- it's at least feasible to slowly transition the US to metric; I believe (?) some sectors of engineering there are already there, and any quantity should always be given with a unit of measurement, so there should be no ambiguity. I can easily mentally switch between drawings with metric and imperial units, no worries at all. Even so, the US still won't switch!

So what hope is there of switching the entire world to electron current; when the average electronic engineer (me included) has a mental breakdown when looking at an upside-down circuit schematic with all the P type fets at the bottom and Vss and Vdd switched around, and current going the opposite way to what the symbol suggests? How do you propose enacting this change, when conventional current is so conventional that, by convention, I can understand a circuit diagram without having to scan circuit diagrams for "This diagram uses conventional current" annotations alongside the "All units in inches".

If anyone ever says "conventional current is wrong", slap them. There's a reason that current is a distinct concept to electron movement.

[Mechatrommer]

Why doesn't the world switch to DC power grid?

how are you going to transfer it to lower potential in an isolated manner?

Why are we still driving combustion cars?

if newer technology battery electric car is more economical bang per buck fuel consumption, i'll switch...

Why don't we abandon the stupid Philips screws for Torx?

for very small screw geometry, you'll know where the Torx problem lie. i dont want to keep buying small torx driver everytime..

if we solved all the problems there wouldn't be any more problems for the next generation to solve. 

in case of this electron convention, metric, left hand right hand etc, i dont have a clear reason except people are too comfortable with what they are used to. when one try to switch convention and got confused by this non-uniform notations, then its a problem that one has to accept to live with, no one bloody cares of this never ending problems, but its a "problem" nonetheless.

[vk6zgo]

The more pragmatic question is; why do people even tell students about electron current in ELECTENG 101? I was fortunate enough to learn electronics with a Dick Smith Electronics kit when I was young; when I went to university I knew to ignore the silly man talking about electrons.

Don't get me wrong, it becomes important in year 3 when talking about the theory of operation of MOSFETs and so on; I just don't get why it's mentioned so soon. It's not like there's any obvious contradictions anymore, like the current flowing from the cold side to the hot side of a vacuum tube.

Just because Vacuum tubes aren't used much anymore doesn't remove the contradiction.

Techs learnt Electron Theory & hence,Flow,for years,but were then told that for Historical reasons,Conventional current was used for all the "right hand rules",etc.
It usually took 16 year olds all of 3 minutes to understand this.---after all,it's not rocket science!!

Engineers,for some incomprehensible reason,get all stressed about the concept of Electron Flow,maintaining that you would have to draw schematics upside down, write Ohm's Law as minus I=V/R & so on.

The beauty of Conventional Current Flow & Electron Flow is that all the voltage drops around a circuit occur in the same polarities,no matter which convention is used.
This means that there is no reason to express current values with either a negative or positive prefix,except when using the rules referred to earlier.

Some texts show current flow symbols without any arrow head.

It is perhaps unfortunate that  the terms Negative & Positive were chosen.
I have seen examples where supposedly knowledgeable people refer to the Positive terminal of a circuit as the "higher" voltage,compared to the Negative terminal.
It is,& always will be, the more Positive terminal.
 

[AndyC_772]

Why don't we abandon the stupid Philips screws for Torx?

You can. Next time you design something that requires screws, use Torx. You don't have to wait for permission, or for everyone else to do the same!

[orolo]

Changing the sign of I in all circuits by convention would make them unphysical. The problem is not the direction of the current flow: in a circuit current flows from high to low potential, as it must.  The problem is that electrons have negative charge, by definition, so they move against gradient. The real question is: should we redefine the new Coulomb as -1 old Coulombs, making the electron positive and the proton negative, owing to electron's greater practical utility to man? If we did so, electrons would move from high to low potentials, and everything else would follow. Fundamental physics would not change by this convention, but practical consequences would be far reaching. We would have to switch the polarity sign in all new batteries, and beware of the old ones, just to give an example. Massive transition costs, quite a bit of chaos.

[Brumby]

What would you do with the diode symbol?  It's very visually indicative of its function under the current convention.

Then, if that were to change, what about the band marking on the components themselves - they'd be at the wrong end!

... and the list goes on.

Massive transition costs, quite a bit of chaos.

... for no real benefit.

[TimFox]

Why doesn't US finally switch to the Metric System?

The United States did switch to the metric system in 1959.  They just didn't tell anyone.  (At that moment, the inch was re-defined from the old spec of 1 meter = 39.37 inch to the current value of 1 inch = 2.54 cm, exactly.)
Just because the legal system in the US is metric does not mean that free citizens have to abandon conventional units.  The conventional units all have legal definitions in terms of the international standard metric units.

Why don't we all add a year zero to the internationally-defined "dominical" calendar system so that centuries start at xx00 instead of the defined value of xx01 (e.g., 2000 was the last year of the 20th century and 2001 is the first year of the 21st century and third millenium).  After all, a survey of high-school seniors (and most anyone else) already believes that.

[vk6zgo]

Nobody is suggesting everything needs to be reversed.

I am quite happy for Electron Flow to be from Negative to Positive,without wanting to steal your beloved + sign.
A complete circuit needs both  +ve & -ve supplies,so it doesn't matter which way current really flows.

As I said before,if 16 year olds in a Tech College course can understand the relationship in 10 minutes,there is no confusion.

[d4n13l]

So, when I was thinking about the question I proposed I realized it applies to multiple other matters as the ones HAL-42b mentions. I guess what I was later more interesting in finding out is how would people working in the field feel about it, since I believe there lies the root at which these things can be dealt with, if there is any.

Also I wanted to see what the opinion of more experimented people would be. I now realize this worked as a sort of social experiment about the the matter, and for what I gather here, would you agree to say that the reason this conventions don't change is because people generally speaking don't want them to? or at least I think that's the consensus here, i.e. there may be some small problems with current conventions (see what I did there?) yet they get the job done so it's not worth updating them so they fit the paradigm they were designed for better? And when I say worth it I mean it would be too expensive, or simply too much of a pain in the butt to update everything.

I guess I see good points both ways. Anyway I know these kind of discussions are exhausting for some people, it just helps me make up my mind about how the world works.

[T3sl4co1l]

https://xkcd.com/567/



Tim

[Rick Law]

Why doesn't US finally switch to the Metric System? Why doesn't the world switch to DC power grid? Why are we still driving combustion cars? Why don't we abandon the stupid Philips screws for Torx?
...
...

Cost and benefit is the measure non-government entities use to decide what to do.  So, the lack of adoption is therefore conclusive that the majority of the US industries found metric system more cost than benefit.

Not only must benefit exceeds cost, benefit must exceed cost by a certain margin.  Let say a typical 401K (retirement) fund invests in S&P500 and gets a (for example) 5% return.  A company that spends a $1 million replacing a yard-machine with a meter-machine and not get $1.05 million back as a result of such upgrade is not spending the money wisely.  It would have earn that $.05 million merely by putting it in S&P500.  I could have use any other funds as example, but 401K and other retirement pensions are together a big percentage of total investments in the stock market.

We are still driving internal combustion engine because it also failed the cost-benefit equation.  Once government (direct or indirect) subsidies disappear, it is doubtful fully-electric cars can exist in the mass market.  Hybrids and specialty market (gulf carts, etc) are different.  They may be able to pass the cost-benefit equation.

[IanB]

it just helps me make up my mind about how the world works

I could read this two ways, and I don't know which way you meant. It could be "how the world works" in terms of people and change, or "how the world works" in terms of physics.

If it is the latter, you should avoid thinking that the equations in physics for voltage and current are in any way "wrong". They are not. They are completely accurate and testable and correct. The only difference to make would be to change all plus signs to minus, and all minus signs to plus. If this were done all the equations would continue to work just the same and nothing actually would be different. Since nothing would be different, making any change would be pointless. It is the pointlessness of the change that explains why has never been done. Why would you do something that is completely pointless?

[d4n13l]

I could read this two ways, and I don't know which way you meant. It could be "how the world works" in terms of people and change, or "how the world works" in terms of physics.

I meant it purely in terms of people and change as you put it.

[CatalinaWOW]

Changing the sign of I in all circuits by convention would make them unphysical. The problem is not the direction of the current flow: in a circuit current flows from high to low potential, as it must.  The problem is that electrons have negative charge, by definition, so they move against gradient. The real question is: should we redefine the new Coulomb as -1 old Coulombs, making the electron positive and the proton negative, owing to electron's greater practical utility to man? If we did so, electrons would move from high to low potentials, and everything else would follow. Fundamental physics would not change by this convention, but practical consequences would be far reaching. We would have to switch the polarity sign in all new batteries, and beware of the old ones, just to give an example. Massive transition costs, quite a bit of chaos.

Best answer by far!

By the way the US began adopting the Metric system in 1866 and has taken several formal steps along the way.  It just hasn't outlawed English units.  The metric system is in common use here.  All automobiles are built metric, and have been for 20 or more years. (My 1982 vehicle was a weird hybrid, with most fasteners metric, but of nonstandard sizes, and a few English unit fasteners).  In most of the sciences metric has taken over.  And many consumer products are sold in metric quantities and almost all are dual marked.  Many athletic events are measured in metric units.

The big holdouts are in the building trades, personal measurements (height and weight), highway related measurements and in the temperature system.  In those areas there are no compelling reasons for change.  Carpenters and plumbers don't do energy and acceleration problems where dimensional consistency is an issue, nor does it really matter if a speed limit is in km/hr or m/hr as long as your speedometer is appropriately marked.  The temperature system has the least reason of all to change.  The only advantage that Centigrade or Celsius has over Farenheit is that the heat capacity of a common material has a value close to one standard unit.  Everything else is arbitrary, and it can be argued that the Centigrade unit is slightly larger than optimum for evaluating human comfort.

The fight over metrification has some curious sidelights.  Things which have been standardized in English units persist in the Metric world.  This forum knows about component lead spacing.  Plywood dimensions are another example.  And as an overall proponent of the metric system for the convenience in keeping track of the difference between force and mass and other similar reasons I am infuriated by how often I see torque values in the metric world specified as g-cm.  Shows that metric can't solve basic understanding of how the world works.

[HAL-42b]

In all honesty, in a country where fuel consumption is measured in miles-per-gallon the speed should also be measured in hours-per-mile, y'know, for the sake of consistency 

[/troll]

[rs20]

...I am infuriated by how often I see torque values in the metric world specified as g-cm...

What's wrong with that? Even if g-cm is not an SI unit of torque, it is 100% blindingly obvious that it means 9.8 mN-cm; and it's also easier for some to intuit about.

[Brumby]

Shows that metric can't solve basic understanding of how the world works.

Lack of understanding of how the world works doesn't come from the measurement system - it comes from ignorance (as in, not knowing).

All the metric system does is give things more accurate definitions - and get rid of a range of awkward conversions, allowing simple decimal calculations.

[CatalinaWOW]

...I am infuriated by how often I see torque values in the metric world specified as g-cm...

What's wrong with that? Even if g-cm is not an SI unit of torque, it is 100% blindingly obvious that it means 9.8 mN-cm; and it's also easier for some to intuit about.

Yeah, and poundals, slugs, pounds force and pounds mass are blindingly obvious to some, and easier to intuit for others. 

[Mechatrommer]

Yeah, and poundals, slugs, pounds force and pounds mass are blindingly obvious to some, and easier to intuit for others. 

but sometime lb.f is simply written as lb which may invite pulling hair event during the design process of a metric guy. but i agree, things like plywood size, plumbing etc should be kept imperial. it'll be akward to say 1.2m x 2.4m plywood or give me 2.54 cm or 1.905 cm pipe. but for temperature, it should be degC regardless. human comfort can be stated in 0.1 resolution... but that just me.

[rs20]

Yeah, and poundals, slugs, pounds force and pounds mass are blindingly obvious to some, and easier to intuit for others.

To be clear, I'm not making a metric vs imperial statement here. I was just defending the use of "grams-force" as a more intuitive alternative to Newtons.

[miguelvp]

Yeah, and poundals, slugs, pounds force and pounds mass are blindingly obvious to some, and easier to intuit for others.

To be clear, I'm not making a metric vs imperial statement here. I was just defending the use of "grams-force" as a more intuitive alternative to Newtons.

Easy solution, let's redefine the gram as 1000 times more than now, so, instead of a kilogram being close to 1dm^3 of volume of water, let's call that a gram. It is convention after all.

The thing is that we as human beings can deal with 1 liter, 1 kilogram, 1 second, 1 meter and the other SI units.

One gram not so much (unless you buy and consume things in grams and then no one cares, well unless is saffron I guess).

But nothing prevents us to shift that by 3 orders of magnitude, the math will still work.

Hey the math works for pounds, it's all arbitrary.

Edit: just to be clear what I meant, if we change the definition of a gram to be the same as a kilogram, then a newton would be 1g x m/(s^2) and the current gram-force will really be a milligram-force and no one will use it

[rs20]

just to be clear what I meant, if we change the definition of a gram to be the same as a kilogram, then a newton would be 1g x m/(s^2) and the current gram-force will really be a milligram-force and no one will use it

Well, obviously it's never going to change, but I take your point that it's unfortunate that the kilogram is basically the base measurement of mass. After all, my edit on this post was totally not me remembering this fact and changing "N-cm" to "mN-cm". Honest. 

[Tac Eht Xilef]

By the way the US began adopting the Metric system in 1866 and has taken several formal steps along the way.  It just hasn't outlawed English units.

The US doesn't use English Units, or even the Imperial system. It uses United States Customary units, which in many cases vary significantly from both the original English system (on which it was based but has since diverged) and the slightly more recent Imperial system.

[AndyC_772]

Could someone please clarify exactly what's meant by "English units"?

Here in England, we use metric. Prior to that, we used Imperial measurements.

I've only ever heard the phrase "English units" used by non-English people, which seems... just odd, really.

[Brumby]

Could someone please clarify exactly what's meant by "English units"?

I'm curious also.  I would have thought it was synonymous with Imperial, but I can't recall having heard the expression before.

[miguelvp]

Could someone please clarify exactly what's meant by "English units"?

I'm curious also.  I would have thought it was synonymous with Imperial, but I can't recall having heard the expression before.

Simple, works for us

I do love the base 2 fractions, very convenient.

[IanB]

Could someone please clarify exactly what's meant by "English units"?

I'm curious also.  I would have thought it was synonymous with Imperial, but I can't recall having heard the expression before.

I think it is an incorrect reference to US customary units. US custom varies of course from the Imperial system particularly in liquid measure, where the fluid ounce, pint, and gallon are different sizes from their Imperial counterpart.

Probably the use of "English" for American measures is similar to the way that you find "English" muffins in the bakery, even though you do not find such things in England.

With the reference to fasteners above it is also worth noting that screw threads are also totally different across the Atlantic as well. America does not use the British standard thread sizes such as BSW, BSF or BA.

[d4n13l]

America does not use the British standard thread sizes such as BSW, BSF or BA.

Just FYI, America is also an incorrect reference to the US.

[IanB]

Just FYI, America is also an incorrect reference to the US.

I'm afraid you are going to lose that one. It is widely accepted in the English speaking world that "America" is short for "United States of America" when the context is a country (and by the way, I am not American).

For the continents we specifically use "North America" and "South America", with maybe "Latin America" in the middle.

[denelec]

Why don't we abandon the stupid Philips screws for Torx?

Robertson screws are far superior to Philips.
https://en.wikipedia.org/wiki/List_of_screw_drives#Robertson
No slippage and the screw stays firmly on the screwdriver at almost any angle.
Unfortunately, they are virtually unknown outside Canada. 

[retrolefty]

US custom varies of course from the Imperial system particularly in liquid measure, where the fluid ounce, pint, and gallon are different sizes from their Imperial counterpart.

 So who knows why there is dual usage of the unit name ounces, as used in both mass and volume. Did they run out of unique unit names? 

 Seriously there must be some historical story to explain arriving at that this seemingly stupid decision.

[IanB]

So who knows why there is dual usage of the unit name ounces, as used in both mass and volume. Did they run out of unique unit names? 

Seriously there must be some historical story to explain arriving at that this seemingly stupid decision.

Sure, I know why. One Imperial fluid ounce of water weighs one ounce. This causes a pint to weigh 20 oz and a gallon (160 oz) to weigh 10 lb. It is simple and convenient.

[retrolefty]

So who knows why there is dual usage of the unit name ounces, as used in both mass and volume. Did they run out of unique unit names? 

Seriously there must be some historical story to explain arriving at that this seemingly stupid decision.

Sure, I know why. One Imperial fluid ounce of water weighs one ounce. This causes a pint to weigh 20 oz and a gallon (160 oz) to weigh 10 lb. It is simple and convenient.

 Maybe you missed my point. Does a fluid ounce of mercury weight the same as a fluid ounce of water?

[Brumby]

Sure, I know why. One Imperial fluid ounce of water weighs one ounce. This causes a pint to weigh 20 oz and a gallon (160 oz) to weigh 10 lb. It is simple and convenient.

The metric system also uses water to define mass: 1 litre of water weighs has a mass of 1kg.

[Brumby]

So who knows why there is dual usage of the unit name ounces, as used in both mass and volume. Did they run out of unique unit names? 

Seriously there must be some historical story to explain arriving at that this seemingly stupid decision.

Sure, I know why. One Imperial fluid ounce of water weighs one ounce. This causes a pint to weigh 20 oz and a gallon (160 oz) to weigh 10 lb. It is simple and convenient.

 Maybe you missed my point. Does a fluid ounce of mercury weight the same as a fluid ounce of water?

No, of course not.  A fluid ounce is a measure of volume.

Water is used as the reference to define the volume/weight relationship.

Thereafter you use relative density (aka specific gravity) for comparison of materials.  For liquids, these are almost always related to the same reference: Water = 1.

[IanB]

Maybe you missed my point. Does a fluid ounce of mercury weight the same as a fluid ounce of water?

So who knows why there is dual usage of the unit name ounces, as used in both mass and volume.

I don't think I missed anything. There is "ounce (avoirdupois)" and "fluid ounce". Different names. When using liquid measure we always say "fluid ounce" and not "ounce". We also use the symbol "fl oz" for liquid measure and "oz" for weight.

If I ask for 10 fl oz of mercury I will expect someone to measure it in a measuring cylinder. If ask for 10 oz of mercury I will expect someone to weigh it. No confusion.

[retrolefty]

Maybe you missed my point. Does a fluid ounce of mercury weight the same as a fluid ounce of water?

So who knows why there is dual usage of the unit name ounces, as used in both mass and volume.

I don't think I missed anything. There is "ounce (avoirdupois)" and "fluid ounce". Different names. When using liquid measure we always say "fluid ounce" and not "ounce". We also use the symbol "fl oz" for liquid measure and "oz" for weight.

If I ask for 10 fl oz of mercury I will expect someone to measure it in a measuring cylinder. If ask for 10 oz of mercury I will expect someone to weigh it. No confusion.

 That is all correct. But wouldn't it be better to use two different unit names for those two cases. Seems a mystery to me, and this is not the first time I've asked for a explanation if there is logic or just convention to the use of using fluid ounces and ounces for two different measurements.

[elgonzo]

For the continents we specifically use "North America" and "South America", with maybe "Latin America" in the middle.

Keeping with the theme of commonly misapplied geographic names with regard to the Americas, "Latin America" is actually not the middle part between North and South America. That part is called "Central America". "Latin America" is the collection of countries of Central and South America speaking predominantly latin/romanic languages (hence the name), which also explains why Belize, Jamaica, Guyana, Surinam and perhaps a few other Central/South American countries are not considered to be a part of Latin America.

[miguelvp]

For the continents we specifically use "North America" and "South America", with maybe "Latin America" in the middle.

Keeping with the theme of commonly misapplied geographic names with regard to the Americas, "Latin America" is actually not the middle part between North and South America. That part is called "Central America". "Latin America" is the collection of countries of Central and South America speaking predominantly latin/romanic languages (hence the name), which also explains why Belize, Jamaica, Guyana, Surinam and perhaps a few other Central/South American countries are not considered to be a part of Latin America.

Since when?

Mexico is definitely part of Latin America and it's in the North American Continent.
Cuba and the Caribbean is also Latin America.
Even Brazil (which speak Brazilian Portuguese) is part of Latin America.
I would even venture to say that Latin America included California, Arizona, Texas, and Florida at least until the Spanish lost them.

[elgonzo]

Since when?

Mexico is definitely part of Latin America and it's in the North American Continent.
Cuba and the Caribbean is also Latin America.
Even Brazil (which speak Brazilian Portuguese) is part of Latin America.
I would even venture to say that Latin America included California, Arizona, Texas, and Florida at least until the Spanish lost them.

Yes, right, Mexico and the Caribbean islands are in NA, but not in Central America. Sorry for excluding the north from the latin party. Doh!

[IanB]

Keeping with the theme of commonly misapplied geographic names with regard to the Americas, "Latin America" is actually not the middle part between North and South America. That part is called "Central America".

Thanks for the correction 

[pmbrunelle]

I do love the base 2 fractions, very convenient.

Base 2 is very much for suited for computers. I'm sure that there are computers using binary to store mm dimensions. So mm (or some fraction of one) are already in base two, just the same as "fractional" inches. The choice of the unit and the base are two different issues.

The metric system also uses water to define mass: 1 litre of water weighs has a mass of 1kg.

Unfortunately, this has not been true for over a century. When the kg was defined as the mass of the International Prototype Kilogram, it stopped being possible for anyone to reproduce the kg in their backyard.

SI doesn't facilitate anything versus Imperial units. It's just an arbitrary re-scaling of quantities.

Besides, now that 1 in == 25.4 mm exactly by definition, inches are really just disguised mm.

So why are electrons "negative" anyway? What does it mean...

[miguelvp]

True and x/32 or x/64 will have an exact binary representation using 5 or 6 bits  of the mantisa respectively.

That's exactly why I meant it was convenient, also it's convenient geometrically for carpenters without the use of rulers and such.

[Brumby]

The metric system also uses water to define mass: 1 litre of water weighs has a mass of 1kg.

Unfortunately, this has not been true for over a century. When the kg was defined as the mass of the International Prototype Kilogram, it stopped being possible for anyone to reproduce the kg in their backyard.

Well, it started out that way - and it's still close (1.000028 litres)

[IanB]

SI doesn't facilitate anything versus Imperial units. It's just an arbitrary re-scaling of quantities.

Actually, it does. It puts similarly dimensioned quantities on a common footing and allows calculations to be done without awkward conversion factors appearing everywhere. The most troubling for new students is the appearance of g_c in many formulas to convert between mass and force (and woe betide you if you accidentally multiply by g_c when you need to divide).

Beyond that, consider calculating the compressor horsepower to compress 100 cfm of air from 15 psi to 100 psi. Suddenly you have got hp, ft, lb_f and minutes all mixed up in one formula. There is going to be a "magic number" in that formula that converts all the incompatible units. You'd better have a good memory for conversion factors. Every formula will have a different magic number in it.

[miguelvp]

The metric system also uses water to define mass: 1 litre of water weighs has a mass of 1kg.

Unfortunately, this has not been true for over a century. When the kg was defined as the mass of the International Prototype Kilogram, it stopped being possible for anyone to reproduce the kg in their backyard.

Well, it started out that way - and it's still close (1.000028 litres)

The international prototype was achieved by equating the mass of 1 liter of distilled water at a bit lower than 4 degrees C  when water is at its highest density at one Atmosphere of pressure, probably at sea level.

That's still true. However there are efforts to change that using Planck's constant as well as the Avogadro initiative.

Edit: but if you make a container that holds 1dm^3 of distilled water and chill it to 3.984 C you'll get a kilo if you are by the beach

[CatalinaWOW]

SI doesn't facilitate anything versus Imperial units. It's just an arbitrary re-scaling of quantities.

Actually, it does. It puts similarly dimensioned quantities on a common footing and allows calculations to be done without awkward conversion factors appearing everywhere. The most troubling for new students is the appearance of g_c in many formulas to convert between mass and force (and woe betide you if you accidentally multiply by g_c when you need to divide).

Beyond that, consider calculating the compressor horsepower to compress 100 cfm of air from 15 psi to 100 psi. Suddenly you have got hp, ft, lb_f and minutes all mixed up in one formula. There is going to be a "magic number" in that formula that converts all the incompatible units. You'd better have a good memory for conversion factors. Every formula will have a different magic number in it.

Exactly.  While the sizes of the units are arbitrary in both systems, the relationships are maintained in the SI system.  A bit of confusion is added when convenience/honor units are added (things like Pascals) but it is still easy to get back to the base units.  And thence my gripe about measuring torque in the units of gm-cm.  You can't multiply gm-cm by rotation rate and get units of power.  You have to remember one of those "magic numbers", and remember that it is necessary.  A step back towards the morass of doing physics in (you pick the name) English/American/traditional units.

[TimFox]

The metric system also uses water to define mass: 1 litre of water weighs has a mass of 1kg.

Unfortunately, this has not been true for over a century. When the kg was defined as the mass of the International Prototype Kilogram, it stopped being possible for anyone to reproduce the kg in their backyard.

The international prototype was achieved by equating the mass of 1 liter of distilled water at a bit lower than 4 degrees C  when water is at its highest density at one Atmosphere of pressure, probably at sea level.

That's still true. However there are efforts to change that using Planck's constant as well as the Avogadro initiative.

Edit: but if you make a container that holds 1dm^3 of distilled water and chill it to 3.984 C you'll get a kilo if you are by the beach

I was taught that the original definition of the gram was in terms of a cubic centimeter of water (at maximum density), and that a liter was defined 1000 cubic centimeters.  When the prototype kilogram became the new definition, the liter was still defined in terms of 1 kg of water, since the chemists needed to use it, and therefore the liter (non-SI unit) is slightly different from 1000 cubic centimeters.  The SI unit of volume is merely the cubic meter, which does not have a name.
There was a non-serious suggestion to name the liter/minute the "Falstaff", in opposition to re-naming the "cycle per second" as the "Hertz".
Well, it started out that way - and it's still close (1.000028 litres)

[hamster_nz]

I'm afraid you are going to lose that one. It is widely accepted in the English speaking world that "America" is short for "United States of America" when the context is a country (and by the way, I am not American).

You wouldn't happen to be from the USA?    "Mexicans are not Americans"    "Brazil is Un-american!"  

(Yes, this is light-hearted trolling, for anybody who misses it...)

Down here we use "The States" to refer to nearly anywhere you have to go through US customs and America is a more generic term for North America... "I'm flying to America for a week skiing at Whistler" would raise no eyebrows.

Hawaii is an odd special case. You should really give it independence and save all the confusion

[rs20]

And thence my gripe about measuring torque in the units of gm-cm.  You can't multiply gm-cm by rotation rate and get units of power.  You have to remember one of those "magic numbers", and remember that it is necessary.

A. That "magic number" is g, which we all know.
B. It's far more common to want to know how much weight a motor can hoist than how much mechanical power it's putting out. If you have a torque in N-cm, you need that same "magic number" (g) to convert the force back into grams!!

My point is, it's context specific; completely rejecting gm-cm is ridiculously inflexible. Please don't pretend that you're objectively right by cherry-picking operations which are easier starting from N rather than grams; I could sit here cherry-picking operations starting from grams and we'd never get anywhere.

[KL27x]

Robertson screws are far superior to Philips.
https://en.wikipedia.org/wiki/List_of_screw_drives#Robertson
No slippage and the screw stays firmly on the screwdriver at almost any angle.
Unfortunately, they are virtually unknown outside Canada. 

The Robertson screw has a different set of compromises, is all. Screwhead must be fairly deep. The bit gets seized/stuck in screw with significant torque (say you are removing a lot of high torque screws.. you may have to tap/wiggle each screw to get them off the bit, similar to a hex head). The angle between the driver and screw must be straight. And the screwhead impression must be in a particular set of sizes.

One of the greatest advantages of Phillips is that you can drive a Phillips head screw with the wrong Phillips head bit. They overlap to a large degree. With one or two Phillips head bits, you can do nearly anything. If you have the wrong size Robertson head, you are SOL. I don't see Roberson as doing anything that hex or torx doesn't accomplish better. (A Robertson "allen key", for instance, would need a room to make at least a 90 degree arc to be useful, compared to a hex head). Also with a phillips, you can also drive a screw at a slight angle between the screw and driver.

And it's known in the USA, just fine. I'm curious if it is actually the most common type of screw in Canada.

[Dinsdale]

    You don't have to change anything. Conventional flow is hole flow from pos to neg. Electron flow is from neg to pos.
They occur simultaneously.

    I always think in terms of electron flow. Current flow is in the opposite direction of all those schematic symbols.
Every tech. I know thinks in those terms. Every engineer I know thinks in conventional mode. It helps the engineers get
their math polarity correct. But I know the polarities because I know which way the current is flowing. Confusing? It
just seems natural to me.

    Just go to the freeway. Look at all the parking spaces traveling South in the North-bound lane. South is the real direction
of travel.

[pmbrunelle]

Robertson screws are far superior to Philips.
https://en.wikipedia.org/wiki/List_of_screw_drives#Robertson
No slippage and the screw stays firmly on the screwdriver at almost any angle.
Unfortunately, they are virtually unknown outside Canada. 

The Robertson screw has a different set of compromises, is all. Screwhead must be fairly deep. The bit gets seized/stuck in screw with significant torque (say you are removing a lot of high torque screws.. you may have to tap/wiggle each screw to get them off the bit, similar to a hex head). The angle between the driver and screw must be straight. And the screwhead impression must be in a particular set of sizes.

One of the greatest advantages of Phillips is that you can drive a Phillips head screw with the wrong Phillips head bit. They overlap to a large degree. With one or two Phillips head bits, you can do nearly anything. If you have the wrong size Robertson head, you are SOL. I don't see Roberson as doing anything that hex or torx doesn't accomplish better. (A Robertson "allen key", for instance, would need a room to make at least a 90 degree arc to be useful, compared to a hex head). Also with a phillips, you can also drive a screw at a slight angle between the screw and driver.

And it's known in the USA, just fine. I'm curious if it is actually the most common type of screw in Canada.

I think the self-holding to the screwdriver is a good feature of Robertson. Makes things less clumsy. If you want to take off a screw that's stuck, I just tap the screwdriver on something.

Robertson is great because of the taper. This means that regardless of tolerances, every screw has a tight fit with the screwdriver. The screwdriver must be straight with the screw; but why would you want to drive it crooked?

There are No. 1, 2, 3 Robertson sizes... same as Philips.

Torx or Allen are not tapered. Obviously, to accommodate manufacturing tolerances, there must be some slack between the screw and the driver. So these are not self-holding like Robertson. In part due to the slack, Allen heads are prone to stripping. Torx does not strip, but it still suffers the non-self-holding malaise.

Robertson doesn't strip like Allen, but it strips more easily than Torx.

Philips is tapered too, like Robertson. However, the taper of Philips is more pronounced, so Philips will cam-out with too much torque. Robertson won't easily cam out, so you don't need to push hard on the end of the screwdriver to get a reasonable amount of torque.

Cam-out for mass production is obsolete. Torque-limited screwdrivers exist now; the cam-out doesn't need to be built into the screw head.

With Philips, it's easy to end-up with busted up screw heads because you cammed out, then you need to go over them with a file to be aesthetically pleasing...

Robertson is common in home construction type stuff. Electrical terminals/connections are going to be slotted or Philips. Automotive is Torx, Allen, or external hex (same as USA).

Robertson is my favorite of all. I think it has the right set of compromises. Looks easy to manufacture.

[IanB]

Robertson is common in home construction type stuff.

But Robertson is more or less found only in Canada. It is not common anywhere else.

[timb]

At least it's better than slotted. Anytime I encounter one, I find myself with a strong desire to travel back in time and curb stomp Johannes P. Slotte when he was just an infant.

At least a Phillips screw can be easily held against the bit with a single finger (or no fingers at all with a magnetic bit), but not a slot! The heads get chewed up easily if the bit is too narrow. Then, I find a bit that's exactly the right width, only to find out it's too thick for the slot in the screw! So I go down a size and chew up the head anyway...

Dumb, dirty, ignorant slots.

[TimFox]

For my woodworking, I have switched to Robertson (square-drive) screws.  The self-holding feature is great.
I use them also for larger machine screws, but there is a much better availability of machine screws in Phillips head.  Recently, I have concentrated on truss-head stainless Phillips screws for electronic assembly.  McMaster Carr is an excellent source for machine screws in all shapes, sizes, and material.
In another thread, I mentioned "Reed and Prince" screws, which were used in classic -hp- gear.  They look like Phillips drivers, but there is only one size driver for several head sizes, and the blades are subtly different.  The only place I could find the drivers was the Sears Craftsman website (but not Sears stores), where they were available for about the same price as "normal" Craftsman screwdrivers.  I haven't found them in hex-drive bits.  If you are working on -hp- gear from 1960 to 1980, I recommend this driver.

[KL27x]

But Robertson is more or less found only in Canada. It is not common anywhere else.

I used Robertson screws to build a fence. I just happened to see them at the local hardware store. And I already had two sets of Robertsons bits without even trying. They just commonly come in bit sets, here, it seems to me. (USA). Yeah, it sure is nice for setting/driving the screws. But I haven't gone out of my way to buy any more. (It was slightly annoying having to liberate the drill when the bit got stuck in the head, but the main reason is the standardization thing).

There are No. 1, 2, 3 Robertson sizes... same as Philips.

There are also many more Phillips heads smaller than that for tiny screws where Robertson doesn't work. But my point was that for the range of screws where Robertson's are used, you need 3 bits. For the same range in Phillips head screws, you can use a #2 screwdriver for practically anything. It might not be ideal, but it will probably work.

To touch back on the OP...
I thought the same thing when I first learned about current. Then I experienced how many arbitrary decisions have to be made in making any circuit and doing any microcontroller programming. I still have a hard time. The direction electrons are flowing is no longer a concern. As with any of the other dozens of arbitrary decisions I have to make every day, if it doesn't work like I thought it would the first time, I would switch the direction/logic/#define and try it again.

[CatalinaWOW]

For my woodworking, I have switched to Robertson (square-drive) screws.  The self-holding feature is great.
I use them also for larger machine screws, but there is a much better availability of machine screws in Phillips head.  Recently, I have concentrated on truss-head stainless Phillips screws for electronic assembly.  McMaster Carr is an excellent source for machine screws in all shapes, sizes, and material.
In another thread, I mentioned "Reed and Prince" screws, which were used in classic -hp- gear.  They look like Phillips drivers, but there is only one size driver for several head sizes, and the blades are subtly different.  The only place I could find the drivers was the Sears Craftsman website (but not Sears stores), where they were available for about the same price as "normal" Craftsman screwdrivers.  I haven't found them in hex-drive bits.  If you are working on -hp- gear from 1960 to 1980, I recommend this driver.

When you bought a screwdriver set at Sears in the 1970s-1980s a Reed Prince screwdriver was included.  I bought a few of these sets because between "friends" and family I was always missing screwdrivers.  This is the first mention I have ever seen of where to use one, so I have two or three that always migrated to the bottom of the toolbox where they couldn't get "lost".  Obviously haven't worked with too much HP gear.

[free_electron]

You want to print all the labels to install in all battery powered equipment to swap the + and - ? And then convince the battery makers to do the same ?

Good luck

[Paul Moir]

And it's known in the USA, just fine. I'm curious if it is actually the most common type of screw in Canada.

In construction, it certainly is, with the exception of drywall screws (Phillips) and plumbing (Slot or maybe Phillips).  The rest get thrown into the garbage.  Electrical is still Roberson, though we now get combo slot-phillips-roberston super-easy to strip cheese grade stuff from the 'States sometimes.  Leviton for example.

It used to be common in manufacturing.  If you look at pre-NAFTA appliances manufactured in Canada, you'll find them used almost exclusively.  You also find them in older tube equipment manufactured in Canada for the Canadian market.

The taper in the Robertson generates an interference for a tight fit, making the fastener an extension of the driver.  This is not available in Allen head or (laughably) Torx.
 
You can drive blacks with reds, reds with greens and greens with yellows.  But it defeats the purpose of the interference fit.

[vk6zgo]

You want to print all the labels to install in all battery powered equipment to swap the + and - ? And then convince the battery makers to do the same ?

Good luck

Sorry,"electron which may be readily dislodged from its associated atom",that is a "straw man" argument.
Nobody has suggested that be done.

I,& many others who learnt Electron Flow are quite content with positive being an "attractive" force for electrons.
Even when my old Employer used "Left Hand Rules" in training material to accommodate Electron Flow,it was never suggested + & - markings should be swapped over.

[Brumby]

In this discussion, I hope nobody is considering changing any reference to connections of, say, batteries.  The terminal with the abundance of electrons ready to jump out should always retain the '-' sign.  If not, then there's a fundamental contradiction right there.

... and I still feel the diode symbol is problematic in any thoughts of change.


Some of the lines of what would change and what wouldn't seem to be unclear.  This also indicates a fundamental problem that has the potential for chaos in an unknown number of situations with an unknown severity - and that is the subject matter that has been built on the current convention, which will be further compounded by subject matter that has been built on that foundation.

At times, we've all seen the difficulty people can have learning about electronics - and the explanations and analogies used to try and make it clearer are built on this same foundation.  While I'm not saying every explanation or analogy - or even the majority of them - will be compromised by a change, the fact that there might be is enough (in my book) to worry about where they might occur.  As an example, I will ask this question: "What impact would such a change have on publications like 'The Art of Electronics'?"

[IanB]

This problem is already fixed with nothing more to do.

If I connect a 10 ohm resistor across a 1.5 V battery then a current of -0.15 A flows from the negative terminal to the positive terminal.

Why is it a negative current? Because it's a flow of electrons and electrons are negative. So the calculations work out fine and there is not even any confusion about the electron charge. It's all done and dusted.

[Brumby]

If I connect a 10 ohm resistor across a 1.5 V battery then a current of -0.15 A

The maths might be OK - but I'm also considering the language. For example:

flows from the negative terminal to the positive terminal.

The 'FROMs' and 'TOs' will need to be reversed, or the sentence structure will not match the concept.


Knowing how it all works out makes it easy to comprehend when looking back, but it's going to confuse the newcomers even more than they are now.

[IanB]

If I connect a 10 ohm resistor across a 1.5 V battery then a current of -0.15 A

The maths might be OK - but I'm also considering the language. For example:

flows from the negative terminal to the positive terminal.

The 'FROMs' and 'TOs' will need to be reversed, or the sentence structure will not match the concept.


Knowing how it all works out makes it easy to comprehend when looking back, but it's going to confuse the newcomers even more than they are now.

You realize I had my tongue in my cheek, right?

But even so, I believe there is nothing wrong with the language. Currents and voltages in circuit analysis must be stated with a direction and an appropriate sign applied. In applying KCL, if I say that the sum of all the currents into a node equals zero, then some of the currents must have a negative sign. It's nothing that newcomers don't already have to figure out.

[Brumby]

You realize I had my tongue in my cheek, right?

Not sure.  Probably too many things happening at this end for me to pick up on such subtleties.


I should probably step .. away .... slowly .........

[vk6zgo]

Electron Flow has been around as a concept for a century or so .

In that time,hundreds of thousands of people learnt Electron Flow & the historical reason for the extensive use of Conventional Current Flow & could move easily between  them as required.
Is the current generation of Engineering students easier to confuse than all of those people?

Electron Flow makes it easier to explain the workings of semiconductor junctions & capacitors,Thermionic Emission & Photo-Emission,& their use in vacuum tubes.
A description of capacitor operation based upon Electron Flow is a lot easier to comprehend than silly analogies using fluid & diaphragms.

An enormous quantity of texts on Electrical Engineering use Conventional Current Flow,& are not going to change anytime soon.
An EE should be at home with both concepts.

There are many things which are Conventions,such as North at the top of maps,"clockwise" rotation,etc.

We still use Newtonian Physics,although Einsteinian Physics exist,we use the movement of the Sun across the sky for Navigation,although we know it is us moving,not our Star,we use a "flat earth" model for some antenna measurements.

[Keyrick]

It all depends on,conceptually, what you are trying to do in regards to the utilization of power.  For instance, most modern automobiles take the negative terminal from the battery and attach to the chassis.  Why?  The voltage drop of the big ass chassis is less than it is on a #14 wire.  In this case, the designers want to control the return current via fuses and switches.  With the negative side of the battery attached to the chassis, more electrons are available to the various devices, scattered all over the vehicle, to be powered, and the control is achieved on the return, not the source.

In older tube (Valve) and early solid state equipment like radios and Hi-Fi equipment, the negative side of the power supply was traditionally connected to the chassis of the device, and control of the circuitry was left to the positive return current that finds its way back to the power supply.  Again, the designer wanted the chassis, a larger conductor than 18 gauge wire used on the positive side, to have as many electrons a possible available to the various devices in the equipment.

This was done on purpose, not on a whim or a coin toss.

In the telecommunications industry, at switching centers, the opposite is true.  These designers, for well over a hundred years, decided that they wanted to place control on the source of electrons instead of on the return path.  So in these switching centers, these thousand amp battery supplies ground the positive terminals to the office ground bar (Chassis).  These -48 volt battery plants (actually, these days it is -52 volts) are what power all of the switches and routers in the center.  This is not always the case in remote sites like a cell location, which also run on batteries, there it can be mixed or negative ground, depending on the equipment.  Some radio transmission equipment that attaches to exterior antennas like negative grounds.  I'm not sure, but I think it has to do with keeping lighting away from the equipment.

Today, many circuits function on very low voltages compared to those in the past, and it does not matter as the current requirements on many devices are so low.  So unless you are talking about battery chargers or power amplifiers, you can do pretty much set your reference (that's what we are actually talking about here) to any thing you want.

So, again, it depends on what you want to do conceptually, when decisions are made regarding circuit design.  The Electron theory is in tact, and the Hole theory can work for you if that is what you need.  Do what works best for the concept of the design.

Rick

[IanB]

With the negative side of the battery attached to the chassis, more electrons are available to the various devices, scattered all over the vehicle, to be powered, and the control is achieved on the return, not the source.

I think you have a big conceptual misunderstanding here. It is irrelevant from an electrical point of view whether the positive side of the battery or the negative side is attached to the chassis. Everything will work just the same either way. There is no "source" or "return" in a circuit.

[Brumby]

+1

(Left me scratching my head, that one did.)

[Rick Law]

Either way, you are abstracting.  It is not as if electronic designers regularly watch a line of electrons flow from the (-) end to the (+) end.  The electron flow or the current flow is as abstract as whether we use C for current and measure it Pma, verses I for current and measure it in Amp.  The math stays the same.

Switching, even if feasible, is not going to make it easier to develop better electronics.  It won't make a bit of difference at all.  Electronic Engineers who fails to grasp this simple abstraction is not going to have any kind of a career in electronics anyhow.

[Keyrick]

With the negative side of the battery attached to the chassis, more electrons are available to the various devices, scattered all over the vehicle, to be powered, and the control is achieved on the return, not the source.

I think you have a big conceptual misunderstanding here. It is irrelevant from an electrical point of view whether the positive side of the battery or the negative side is attached to the chassis. Everything will work just the same either way. There is no "source" or "return" in a circuit.

If you accept the theory that electrons flow from negative to positive (Electron Theory) then there is no misunderstanding on my part.  If you connect a conductor to the metal frame of a vehicle, the size of which is tens to hundreds of times larger than a 4 mm wire, you must agree that the voltage drop from one end of the vehicle frame to the other will be less than it will be on the 4 mm wire, especially as current requirements increase.  It is. Not by very much, but it is.  If the voltage drop is less on the frame, then the source of the power (Electrons), (Electron theory) available must be higher than it would be on the 4 mm wire. 

If you are not aware of Source and Return when it comes to power circuits, you may want to investigate those terms, as they are used in large battery plant designs.  Some times "Battery" is used instead of "Source".  Sometimes "Ground" is used instead of "Return". You may not use these terms on your Arduino project, but they do exist in DC power plant design.

As I said earlier, the designers didn't just flip a coin to decide on the best way to distribute power in a particular instance.  The Physicists looked at the concept, saw what work needed to be done, and made a decision based on the known science.

[Brumby]

If you connect a conductor to the metal frame of a vehicle, the size of which is tens to hundreds of times larger than a 4 mm wire, you must agree that the voltage drop from one end of the vehicle frame to the other will be less than it will be on the 4 mm wire, especially as current requirements increase.  It is. Not by very much, but it is.  If the voltage drop is less on the frame, then the source of the power (Electrons), (Electron theory) available must be higher than it would be on the 4 mm wire.

Do I even bother pointing out the GLARING HOLE in this argument?

[Brumby]

... or would I just be feeding a troll?

[Keyrick]

I can assure you that I am no troll.  Hole.  Cute. 

When I was in college in the 1960s, the Electron Theory was pretty much considered settled science.  It was the way we were taught.  In the late sixties, the Hole Theory started to gain some acceptance as a "Out of the Box" way to explain certain things in a different way that some found easier to understand, without getting too deep into the physics.  And it made for a logical way to explain these new fangeld things like solid state (transistor) gates.  As someone said earlier, it doesn't matter either way, the math works out the same.

As the Electron Theory was considered settled science, many engineers used this settled science deciding the proper way to efficiently deploy electrical devices.  Therefore in certain disciplines, certain methods were deemed proper.  In the automobile example, the reason one of the battery conductors was connected to the chassis was that is was an effective method to partially distribute power.  As the settled science at the time was the Electron Theory, (current flows from negative to positive), the negative side of the battery was chosen to be connected to the chassis.  Why?  Since it was the largest electrical conductor in the vehicle, as more devices that required power (lights, turn signals, radios, starters, fans) would suffer less voltage drop as the current requirements increased when one side of these devices were connected to the chassis, and these devices were used at the same time.  And it saved a lot of money because you only needed to run one conductor to a specific device as the other conductor was already there at the chassis.  Of course it works the other way as well, but that method (the Hole Theory) was not considered settled science at the time, in power distribution circles.  And when decisions are made like this in any industry, you needed to have the settled science on your side or you would not last very long, because the bean counters didn't care, they were only concerned with consensus of the scientific community.  If something went wrong, your behind was covered because you agreed with the consensus of the scientific community.
   

I spent 37 years as a power engineer before I retired.  Today I am a hobbyist, mainly working on old tube amplifiers. 

The question was asked "Why not change conventional current (Hole) to electron current? (Theory)"  I was providing information on the history of why the decisions that were made, were made.  And in certain disciplines, the Electron Theory is the preferred method used to explain the operation of specific devices.  So the question is not really valid as I believe the OP was under the impression that the "Conventional Current" method is the only way that these concepts are explained, and it is not. 

Rick

[AndyC_772]

[Just for the sake of anyone else reading this discussion, who may be in danger of being confused or misled]:

Current flows in loops, from the battery, through a conductor, then through the load, then back to the battery via another conductor.

Each conductor has resistance, and the resistance of a car body is indeed likely to be less than that of a length of wire, but the choice to connect it to the terminal marked '-' rather than the terminal marked '+' doesn't make any difference whatsoever to the voltage across the load.

Why? Because the load, the wire and the car body are all electrically in series. The voltage across the load equals the voltage across the battery, minus the voltage drop across the wire, minus the voltage drop across the car body.

If the battery voltage is exactly 12.0V, then in the "negative earth" case the voltages at the terminals of a moderate load (measured with respect to the '-' terminal of the battery) might be +11.5V and +0.1V, and in the "positive earth" case they'd be +11.9V and +0.5V.

In both cases, the voltage across the load is 11.4V. This figure is exactly the same, regardless of which part of the loop is formed by the car body and which part of the loop is formed by the wire.

because the bean counters didn't care, they were only concerned with consensus of the scientific community

I've never once heard of any case in which bean counters know, or care, about the consensus of the scientific community.

then the source of the power (Electrons)

Noooooo!!!!

Electrons are not the source of any power; the chemical reaction in the battery is.

In the late sixties, the Hole Theory started to gain some acceptance as a "Out of the Box" way to explain certain things in a different way that some found easier to understand, without getting too deep into the physics

For what it's worth, a 'hole' isn't quite the same thing as the absence of en electron. In a semiconductor, a 'hole' is (specifically) the absence of an electron in one of the inner orbits around the nucleus; electrons in this band are more tightly bound to the nucleus than the 'free' electrons which carry current more like those in a metallic conductor.

The different energy levels are important. Conduction by holes is less efficient because of that tighter binding between electrons and nuclei in the inner orbits; it takes more energy to strip an electron from its nucleus. This is why P-channel transistors are generally inferior to their N-channel counterparts.

Under the right conditions (which are to do with the respective energy levels of electrons and holes, and the 'band gap' of the material in question), electrons and holes can recombine, and the energy which was originally put into the electron to strip it from its nucleus is released in the form of a photon of light. This is how an LED works.

Conduction by holes doesn't happen in metals, though. They're a semiconductor phenomenon.

[Keyrick]

because the bean counters didn't care, they were only concerned with consensus of the scientific community

I've never once heard of any case in which bean counters know, or care, about the consensus of the scientific community.

You and I live in different worlds!  Where I live, bean counters want 5 nines, and if you could not provide it, they want to know if you are using standard norms(scientific consensus), and if not why?


Electrons are not the source of any power; the chemical reaction in the battery is.

In this discussion, a battery was used as a power source.  A generator or a solar panel could have been used as well.

In the late sixties, the Hole Theory started to gain some acceptance as a "Out of the Box" way to explain certain things in a different way that some found easier to understand, without getting too deep into the physics

For what it's worth, a 'hole' isn't quite the same thing as the absence of en electron. In a semiconductor, a 'hole' is (specifically) the absence of an electron in one of the inner orbits around the nucleus; electrons in this band are more tightly bound to the nucleus than the 'free' electrons which carry current more like those in a metallic conductor.

The different energy levels are important. Conduction by holes is less efficient because of that tighter binding between electrons and nuclei in the inner orbits; it takes more energy to strip an electron from its nucleus. This is why P-channel transistors are generally inferior to their N-channel counterparts.

Under the right conditions (which are to do with the respective energy levels of electrons and holes, and the 'band gap' of the material in question), electrons and holes can recombine, and the energy which was originally put into the electron to strip it from its nucleus is released in the form of a photon of light. This is how an LED works.

Conduction by holes doesn't happen in metals, though. They're a semiconductor phenomenon.
[/quote]

Semiconductors are not everything! I was talking about power distribution and how it is/was referenced.

[Brumby]

... and you still didn't get it right.

Each conductor has resistance, and the resistance of a car body is indeed likely to be less than that of a length of wire, but the choice to connect it to the terminal marked '-' rather than the terminal marked '+' doesn't make any difference whatsoever to the voltage across the load.

Why? Because the load, the wire and the car body are all electrically in series.

Exactly.

But you missed mentioning one - rather critical (especially lethal to your argument) - part of the circuit:

The voltage across the load equals the voltage across the battery, minus the voltage drop across the wire, minus the voltage drop across the car body.

A point, I might add, you completely ignored in your response to AndyC_772's post.

[tszaboo]

We don't want to change to have the ground on the top. Because with the ground on the top, than we than need to walk our hands. That would be ridiculous now, wouldn't it? So that is why the GND is on the bottom, and current flows that way.

[Electric flower]

Sweden day after switching from left to right hand traffic

[TimFox]

Short-form answer:  Physics works at both the macroscopic and microscopic level.
"Current" is a macroscopic phenomenon, and can flow in either direction across a specific boundary.  Polarity definitions (on current, voltage, etc.) must be consistent and agreed to make useful calculations.
"Electrons" are a microscopic phenomenon.  Charge carriers forming current can be electrons with negative charge, holes with positive charge, protons with positive charge, etc.  The product of charge density (scalar) times velocity (vector) times boundary area gives current density (vector).
The accepted definitions of polarity are experimentally consistent, and there is no need to change them on a whim.

[tszaboo]

Short-form answer:  Physics works at both the macroscopic and microscopic level.
"Current" is a macroscopic phenomenon, and can flow in either direction across a specific boundary.  Polarity definitions (on current, voltage, etc.) must be consistent and agreed to make useful calculations.
"Electrons" are a microscopic phenomenon.  Charge carriers forming current can be electrons with negative charge, holes with positive charge, protons with positive charge, etc.  The product of charge density (scalar) times velocity (vector) times boundary area gives current density (vector).
The accepted definitions of polarity are experimentally consistent, and there is no need to change them on a whim.

To be honest, I never seen an electron. I really don't care which way they flow. So it is not proper physical model, and physicist have headaches. If I connect a battery the right way, the current will flow the right way, and the circuit will work. It takes an engineering brain to comprehend that this is a compromise, the very thing that an engineer will need to do every single day.

[TimFox]

In my physics education, I have "sensed" (if not "seen") electrons (and other charged particles).
1.  Millikan oil-drop experiment:  measured discrete changes in charge on small oil drops.  (At the University of Chicago, I used antique equipment originally built for Professor Robert Millikan himself.)
2.  Shot noise in vacuum diodes:  statistics of individual electrons vs. diode current.
3.  Beta decay:  counting individual electrons emitted by nuclear disintegration.
4.  Ion beams.  Counting individual protons that have been accelerated through a vacuum to a detector.

Of course, one does not see the electrons involved in current through a copper wire.  The current is not single electrons zinging down the wire, but a slight tendency for each of a zillion electrons to move in the appropriate direction.

[AndyC_772]

In my physics education, I have "sensed" (if not "seen") electrons (and other charged particles).

You poor deprived soul. Buy me a beer and I'll post you some 

[CatalinaWOW]

In my physics education, I have "sensed" (if not "seen") electrons (and other charged particles).
1.  Millikan oil-drop experiment:  measured discrete changes in charge on small oil drops.  (At the University of Chicago, I used antique equipment originally built for Professor Robert Millikan himself.)
2.  Shot noise in vacuum diodes:  statistics of individual electrons vs. diode current.
3.  Beta decay:  counting individual electrons emitted by nuclear disintegration.
4.  Ion beams.  Counting individual protons that have been accelerated through a vacuum to a detector.

Of course, one does not see the electrons involved in current through a copper wire.  The current is not single electrons zinging down the wire, but a slight tendency for each of a zillion electrons to move in the appropriate direction.

And you can do related experiments to count photons, while other well known experiments prove their wave nature.  At least when I was taking quantum physics the same equations applied to both electrons and photons, but mass and hence wavelength differences make the observables different.  We probably don't really understand the fundamental nature of our universe, we just have models that work pretty well under a variety of controlled conditions.  Why don't we just argue how many angels can stand on the head of a pin?  Has just as much value.  Actually it is fun to visualize moving the internet back to the time when they were argueing about angels and pin heads.  The flame wars would have been intense.

[TimFox]

This was not the official dogma I learned, but I decided that "wave" and "particle" are mathematical descriptions.  When describing reality, one or the other is more appropriate, depending on what is being observed, to calculate the result.  The calculated results can be very accurate when compared with experiment.

[T3sl4co1l]

I swear guys, I've shined a flashlight inside every vacuum tube I've looked at!  Nothing but vacuum in there!  Electrons don't exist!

Tim

[Keyrick]

... and you still didn't get it right.

Each conductor has resistance, and the resistance of a car body is indeed likely to be less than that of a length of wire, but the choice to connect it to the terminal marked '-' rather than the terminal marked '+' doesn't make any difference whatsoever to the voltage across the load.

Why? Because the load, the wire and the car body are all electrically in series.

Exactly.

But you missed mentioning one - rather critical (especially lethal to your argument) - part of the circuit:

The voltage across the load equals the voltage across the battery, minus the voltage drop across the wire, minus the voltage drop across the car body.

A point, I might add, you completely ignored in your response to AndyC_772's post.

Brumby my friend, I didn't ignore Andy's quote.  I agreed with everything that he stated that I didn't quote.  What I did quote, were the issues that I responded to.

I also agree with your statement "The voltage across the load equals the voltage across the battery, minus the voltage drop across the wire, minus the voltage drop across the car body.
[/quote]

My point was that the VD across the wire will be different than the VD across the car body, because the wire will have a higher resistance than the car body.

But you got me to question my theory, so I will create an experiment, using a large wire, say a number 2, and a smaller wire, say a number 14, along with an incandescent bulb, and attempt my measurements across those two wires with current flowing.  Number 14 copper wire has a resistance of .253 ohms per hundred feet.  Number 2 copper wire has a resistance of .016 ohms per hundred feet.  I will try to create these parameters on my bench to see if I can measure a difference.  If there is no difference then I will take back what I said.  If there is a difference, perhaps we can have another discussion.

Best regards.

Rick   

[Brumby]

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.

[Keyrick]

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 

[Brumby]

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.

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.


Do you agree that this is an accurate statement?

[IanB]

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.

This is not a premise, this is a predictable fact. It follows from the simple application of Ohm's law.

However, that's not what you said. You said that making the big conductor negative would produce different results from making the big conductor positive. It wouldn't.

[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.