Why positive ground?

Electron flow is from negitive to postive when dealing with DC current in welding resistance applications. In welding terms this is called straight polarity.

Reverse polarity is when the electrode is positive and the work piece is negitive.

With using straight polarity while welding, metal is transfered from the electrode (negitive) to the work piece (positive) (also called base metal) where alot of heat is generated on the work piece. This lets us use a cooler electrode and transfers alot of metal very fast to the work piece.

Using straight polarity works well as the work piece in this case absorbs more heat than the electrode and can handle more heat input than the electrode as the work piece has more mass than an electrode.

The same can be said of positive ground battery systems. Most of the heat will be generated in the tractor frame and not in the electrical componet. Since heat is a killer to componets of most electrical devices then a positive ground systems should last longer.

I think if you did a side by side comparrision, positive ground compnets will by far out last negitive ground componets.

Like Mark (txblu) pointed out, until the inventors of transistors changed there thinking of electron flow, the transistor could not work. In electronic semi-conductor circuits electron flow is always positive to negitive.

T_Bone

Thanks for the recognition, but I need to rearrange one comment. Having been educated in both electron flow electronics and hole flow electronics, I can see the reasoning for each.

In troubleshooting circuits, electron flow is the easiest to understand; like the Armed Services teaches. When you start designing electronic circuits, you start with a power supply and start hanging things off it. Iffin you're going to do that, to start from the positive (+) terminal of the PS and move out into the circuit, you gotta use words that will go along with that process.

So these brilliant whizbangs decided that if we talk about what happens when an electron moves INTO the positive terminal of the power supply, having been OMITTED FROM the PS neg (-)terminal and having gone thru the electrical components, we can talk flow from the + terminal.

So if electrons are being returned to the power supply via the pos terminal, the ABSENCE of electrons (i.e. the HOLE where one just left)is going out the pos terminal in the opposite direction.

So since colleges prepare engineers, and engineers design things, engineers are taught what the HOLE is doing, rather than what the electron did and hence positive conductance.

And sir, "that's the rest of the story" (Paul Harvey).

Best,

Mark

There are the theorys of electron flow vs current flow, but in practical application it makes no difference.

As was well put below, it's just the way the engineers did it. I think GM was one of the early ones to go negative ground and Chrysler was one of the last.

I've asked old-timers who worked on electronics of the '40's & '50's why the change? Mostly no one is sure, but it may have been that GM was negative ground and in those days GM was something like 60% of the automotive industry. Electrical accesories were becoming more common, so designers went with what the biggest force in the industry had. The rest just followed suit.
But, remember that is just a theory too.

Part of the 12v thing was to crank the big Caddies (500 cu v8's) and other's . Think they had an 8 volt first and then went to 12.

Ask Dell,

He knows.

Mark

Neg ground came about with the transistor radio (for automobiles) and 12 volts in the '50's and inparticular the Germanium transistor they used for the output device. These were PNP doped devices requiring a negative power source for the collector as it was P (+) material and needed to be reverse biased by a (-) power supply.

Since this was a 5 watt device (really large power dissipation for the early days of solid state) they wanted to make sure it was heat sunk good.

Apparently they hadn't perfected good insulators with good thermal transfer characteristics, so they decided to hard mount the transistor to the heat sink chassis. The heat sink was a large finned hootus and was attached to the radio's chassis which was attached to the dash metal, which was attached to the auto's body, then frame.

And (according to Dell.....as I recall) that folks,..... .is the rest of the story (Paul Harvey).

Mark

And in the telephone business, anything still manufactured that is DC powered still is positive ground. I don't know why. But I do know that reversing polarity from -48VDC to +48VDC for even the shortest period of time before can cut the breakers has bad results. "Hello Boss? The good news is that I'm not a heart surgeon, but the bad news is that no one in the whole town of...".

I guess it's all how you look at it.

OK-AL

But you're absolutely right about the cost savings by using 12 volts vs 6 volts.

OK-AL