Why positive ground?

[oj]

What was theory as to having positive ground and what compelled manufactorors to switch to negative ground?
If I recall electrical theory right the voltage flows from positive to negative while current flows from negative to positive.
Any thoughts?

[Jack E/NJ]

Telephone companies originally discovered that copper wiring corroded faster in negative-grounded systems due to electrolysis. So they switched to positive-ground to protect the wires at the expense of whatever metals were connected to the positive ground. This is called cathodic protection (wires connected to the negative battery terminal). So, for an automobile, which would you rather have? Its wiring negative like the phone companies? Or its body negative like the car companies? 8^)

Jack E/NJ

[rotorwrench]

Direction of electron flow was the reasoning behind the positive earth for low voltage systems like all the 6-volt cars were. The 6-volt system is taxed by any resistance in an electrical system. This is why the average wiring is 16 to 10 wire gauge instead of the smaller gauges used in the 12-volt systems. The 6-volt systems needed all the help they could get and flowing electrons directly to the electrical load was as efficient as it got.

In a 12-volt system it's not necessary. Resistance has a much lower effect than with the lower voltages.

[51 MERC-CT]

Not knowing the answer I asked an 8 year old and he replied "because",
and that's good enough for me.

[Mike51Merc]

I had heard, and I'd love to know for sure, that cars were wired with positive ground to help prevent corrosion of the body and chassis. They switched to negative ground because they learned it was better (for the manufacturers) to have the cars rot out so they could sell more cars.

[Jack E/NJ]

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I think it's the other way around. The phone companies wanted to protect the wiring by making them more negative than ground. The car companies wanted to protect their bodies by making them more negative than the wiring.

Jack E/NJ

[Ken Bull]

I always thought it was because Henry Ford was friends with Thomas Edison. Can you imagine there discussions?

[mrtexas]

Originally Posted by rotorwrench

Direction of electron flow was the reasoning behind the positive earth for low voltage systems like all the 6-volt cars were. The 6-volt system is taxed by any resistance in an electrical system. This is why the average wiring is 16 to 10 wire gauge instead of the smaller gauges used in the 12-volt systems. The 6-volt systems needed all the help they could get and flowing electrons directly to the electrical load was as efficient as it got.

In a 12-volt system it's not necessary. Resistance has a much lower effect than with the lower voltages.

What a reason for direction of electric current flow! Modern science has proved that current does not flow from negative to positive as originally thought. Poor old Ben Franklin guessed wrong and we have stuck with him. Doesn't really matter in a practical sense though. We define electric current to be the opposite direction of electron flow. Confused?


http://blog.sciencegeekgirl.com/2009...-current-flow/

“In the past when I taught electricity I always understood that it flows from the negative terminal to the positive. The CPO books and materials have the opposite – from positive to negative. This doesn’t make sense to me in how you generate the flow of electrons, pulling to the opposite charge. Is the book wrong or have I forgotten stuff? 8th grade teacher”

It depends on what you define as “electricity”. Do you mean the flow of “electrons” or the flow of “current”? Because, due to an unfortunate quirk of history, the direction of *current* flow is opposite to the direction of *electron* flow. Take a moment and re-read that, because it’s not what you would expect. If electrons are flowing to the right across this screen, then we say that current is flowing to the left.

[Jack E/NJ]

A current of electrons flows. 8^)

Jack E/NJ

[qmdv]

My old Bug Eye Sprite was 12 volt positive earth. The later cars by the some company went to negative earth.

Tim

[rotorwrench]

There were a lot of misconceptions back in the late 20s that are a lot more clear today. The Model T cars were mostly 6-volt negative ground. When Ford made the change over to the Model A, they were concerned about the way the new ignition system was going work, whether the battery charge would leak through the body to ground, and anodic/cathodic reactions with the body parts. All this stuff was part of the reason that they went to positive ground. Thomas Edison and Henry Ford may have had discussions about the subject since they were close friends but I would be relatively certain that the common consensus of the engineers was to make that change. We have since gained a lot more knowledge in the field that has rendered the worries they had back then to be baseless now.

They were just doing what they thought was best and the least expense at the time. By 1955 they knew that the polarity was not worth worrying about and that modern accessories were going to require 12-volts to get by with minimal warranty concerns and expense.

[42guy]

I had 2 Triumphs and a Jag. All 12 volt and positive ground.

[petehoovie]

Electron flow/current flow....It's all 'theory'.....

[qmdv]

Originally Posted by 42guy

I had 2 Triumphs and a Jag. All 12 volt and positive ground.

NONONO, It is "positive earth" for the Brits

Tim

[George/Maine]

I think when they started using radios with transistors they had to make a standard and went to 12 volt better starting less amps and Neg Ground. They may have never changed if not for that. I have a 54 ford someone changed to 6 volt neg grd and all works good, I don't see any need to change it over to pos grd.

[scooder]

Over here in England we kept positive ground (earth) till about 67-69. Not all companies changed at the same time. But 6 volt was gone way before then, last stuff was Ford with the Popular (Anglia) in 59ish. All the other Fords were 12 volt from 51ish.
Martin.

[Karl]

Originally Posted by scooder

Over here in England we kept positive ground (earth) till about 67-69. Not all companies changed at the same time. But 6 volt was gone way before then, last stuff was Ford with the Popular (Anglia) in 59ish. All the other Fords were 12 volt from 51ish.
Martin.

My Series V Sunbeam Alpine was the first Series of Alpines to go negative earth in 1967-Karl

[JM 35 Sedan]

Originally Posted by oj

What was theory as to having positive ground and what compelled manufactorors to switch to negative ground?
If I recall electrical theory right the voltage flows from positive to negative while current flows from negative to positive.
Any thoughts?

If I recall electrical theory right, voltage does not flow at all, it is just a potential. Only the current flows.

[w4jeh]

John is correct. Current flow is the flow of electrons through a conductor from one point to another. Current flows from negative to positive in A DC circuit.

Voltage doesn't "flow" it's the potential difference between two points in a circuit.

Jim

[scooder]

Originally Posted by Karl

My Series V Sunbeam Alpine was the first Series of Alpines to go negative earth in 1967-Karl

You got an Alpine, nice. I work predominantly on British sports cars from late 50's through late 70's, just finishing an engine rebuild on a MGC, now out of all of these Brits the Alpine is the one car that feels just perfect when I'm sat behind the wheel. Everything is in the right place for me, always makes me grin like an idiot when I'm "road testing" them, they just fit me perfectly. I'm 5'3", so take that into account.
Don't get me wrong, a nice 4.2 early E type Jag (XKE) is an amazing thing to drive, everyone should have a drive of these in there life, but the Alpine just fits me perfectly. And the Alpine looks right from every angle. Much better than the regular MGB'S.
Sorry for going off topic.
Martin.