positive ground

could someone please explain the purpose of positive ground on the electrical system of a tractor. any sites to go to also.
larry cook

It works just as good as negative ground, not much better, not worse. Lots of 6 volt vehicles were positive ground. Nothing really odd about it, just doesn't fit the thinking using solid state NPN transistors. Edison's DC power systems used 110 volts + on one side of the line, and 110 volts negative on the other side. And with wound field motors and lights it doesn't matter what the polarity is. Deere 24 diesel tractors of the 50s and 60s used split 24 volt systems that gave on 12 volt positive ground system and one 12 volt negative ground system. And they worked, still work except for those who can't fathom them and mess them up.

Alternators are very picky about polarity, radios are very picky about polarity. But both have been made with adjustable polarity. Generators and lights are not, so long as the generator is polarized to make it build in the right polarity to match the battery.

Ignition coils are a little picky about polarity, having the right polarity gets a bit better ignition in difficult conditions.

The biggest arguments about polarity concerned corrosion at ground connections, but they are opposite for the battery cable while charging and while starting, and opposite between the battery cable and the starter and generator mounting.

Fact is, Ben Franklin guessed at the polarity of electrons (that he didn't know about) and we have been stuck with that polarity definition. Had he guessed the other way, our positive ground would be negative ground and either way would STILL work. Just you have to keep the polarity in mind when hooking up some stuff.

It won't go away, just live with it.

Gerald J.

It's sort of like cat and dog, Ford and Chevy, IH and Deere.

Different folks like different things/ideas.

guess i could have been mores specific. merely wondering about the thought process behind positive ground. who, when & why? thanks for your response and i imagine we will live it as i have a tractor with pos. ground and have not and will not mess with it.
larry cook

That question was asked awhile ago and I recall someone opined there would be less corrosion with a positive ground system..........I also recall someone thinking the electron theroy seem to "work better" that way?? Somehow I don't think I'll buy that one though.................

Back to day one it was that DCcurrent flowed to Pos gnd. ARMY SCHOOL in FT.NJ taught by GE and RCA instructors showwed and proved in school that current wants to flow to pos gnd and tons of stuff even lots of 12v systems used pos gnd.

Ya,all the Olivers that had a generator,even the newer 12 volt systems were positive ground.

I think what you mean to say is "electrons actually flow from (-) to (+)", which, in reality, has NOTHING to do with choosing to connect either the (+) or (-) battery terminal to chassis ground!
ONE thesis

Like Gerald said, it doesn't really matter. It used to be taught that electricity flows from positive to negative, and as far as I know it's still taught that way in the military schools. But for a long time engineering schools have taught negative to positive because negative polarity fouls up the math. So pretty much any system designed in the last fifty years is going to use negative ground for the simple reason that electrical engineers think that way.

I used to train military technicians on maintenance and repair of weapons systems. The particular system was a mixture of analog and discrete logic components, and of course they were designed by engineers who thought "positive to negative". I found it impossible to communicate to the technicians how to follow the logic of the circuit using the "negative to positive" convention they were familiar with. But then I told them. "OK, forget everything you learned in school: For now, current flows positive to negative." I was then able to explain the logic and they immediately grasped it. Now that may be a reflection on how bad of an instructor I was, but I know that I permanently corrupted several techs who never thought "negative to positive" again.

It seems it is in what we assign stuff. There is nothing in the laws of physics that has "positive" as a red color or "negative" as a black color. They are simply opposing polarity that had to be given a name we could understand. It is good it is more universal since most of us are "programmed" that red is positive.

There are two competing theories of electric flow - the Electron Theory and the Hole Theory. They have electricity flowing opposite directions and neither theory has ever been proven.

At one time, engineers that favored the Hole Theory favored postive ground, and engineers that favored the Electron Theory favored negative ground. Some engineers designed electrical systems on cars and trucks to have both grounds with an automatic "polarity changer."

When semiconductors came into common use - one standard had to be chosen for consumer good.

Postive ground is still used in many applications and, in some, prevents certain types of corrosion - especailly in some marine-military applications.

None is better overall, but each is slightly better for certain uses.

And, nobody knows which way electricy flows - that's why it's called "theory." Otherwise, it would be the Electron Hypothesis or Electron Rule.

There is no argument for either polarity that will hold water based on theories of current flow. Its convenient to think current flows from positive to negative, though we are pretty sure electrons do most of the work in electric circuits in metals by moving the other direction. Holes are only a factor in semiconductor crystals. Mathematically figuring positive to negative flow works out just as accurately as thinking negative to positive. Just keep track of the signs (and the units when mixing metric and imperial units).

There have been historical arguments but there were equally strong opinions for the opposing polarity at the same time. And engineers willing to put a whole car company on the line for their particular polarity. And both worked with no better or worse performance. The articles espousing either polarity will be found in articles from the Society of Automotive Engineers probably during the 1920s and 1930s.

I've worked with both polarities in electronics and vehicles so neither bothers me, or excites me.

There are two fundamental laws that work, no matter what. 1: The sum of the voltages around a closed loop is zero. E.g. the voltage rise in sources exactly equal the voltage drops in loads and wires.

2: The sum of currents though a node is zero. E.g. all the current that goes into a connection, leaves that connection, whether there are two connections to that node or a billion.

ALL circuit analysis is built on these two fundamentals. And it works every time and matches all experiments.

Gerald J.

Yes I never really heard why we had positive ground systems years ago or even why we switched.

What ticks me off is when someone says they have to jump a positive ground system that you have to reverse the jumper cables. When I tell them you hook pos to pos and neg to neg they want to argue. Duh!! So I let them hook it up the way the think and wow do they see sparks!!

One thing to remember when jumping any pos or neg ground system always hook the batteries up to like terminals.

Ground doesn't always mean negative either!!

When disconnecting a battery always disconnect the ground cable first. Be it Pos ground or Neg ground.

The reason for this is you are more likely to touch the frame somewhere when disconnecting either cable but if the ground is hooked up and you are on the opposite battery post and touch the frame with the wrench, the wrench will turn red.

If you're disconnecting the ground cable first and the wrench touches the frame no sparks will occur.