# Positive Ground

Discussion in 'Beginner Electronics' started by Ernie Werbel, Jun 19, 2006.

1. ### Ernie WerbelGuest

Hi all. I am a part-time college student majoring in Electrical Engineering
Technology. I have been trying to learn as much as I can on my own since I
was twelve; about ten years now. The earliest material I found was in books
and experience in taking things apart. I learned that electrons flowed out
of the negative terminal of the battery, through the circuit components, and
back into the positive terminal. Hence, I have always designed my projects
around a positive ground point. No problems there.
Well for the past year I have finally gotten into the hardcore
electronics-related classes at the college. Some material is familiar, but
most of it is new. I am doing well however I have difficulty with the fact
that the modern textbooks are showing the circuits using a negative ground.
This seems backwards. I know the circuit will still work the same way, but
it's hard to get myself to think in the negative-ground sense. If I look at
a positive-grounded circuit, I can envision the electrons and make
calculations without difficulty, but it's a different story with negative
ground for me.
What is anyone else's takes on this?
Ernie

2. ### defaultGuest

Can't you just assume they go from positive to negative, for the
purpose of reading the schematics easier? Frankly I don't see what
the difference is - I know the trons come from ground but that
information isn't relevant to designing stuff.

3. ### James T. WhiteGuest

Ernie,

You, like all EE students that have gone before you, will just have to
accept the way +, - and the positve direction for current are defined.
Once you recognize that it is arbitrary and doesn't really matter so
long as you are consistent, it gets a good bit easier.

The definition of the positive and negative in an electrical circuit was
originally done by Ben Franklin long before the electron was discovered.
At that time he and others understood like charged objects were
repelled, unlike charged objects were attracted and something flowed
when they allowed unlike charged objects to touch. They also understood
that there was an excess of something on one of the objects that was
equalized when you allowed objects to touch. With a 50-50 shot at
getting it right, he just picked wrong when assigning the + and -. By
the time that electons were discovered and found to be the primary
current carrier in wires, it was far too late to re-define + and -.

Now, just wait until you start learning about semiconductor theory and
hole flow.

4. ### Dan HGuest

The assumed current flow and ground are really 2 different issues. As
the others have stated, the direction of current flow is by standard
convention from + to -

Ground is a reference point for measuring other voltages and has
nothing to do with the direction of current flow. It is the zero
voltage point so the if a measurement is -12V it is 12 volts more
negative than ground. If it is +5V it is 5 volts more positive than
ground. there is no reference to current flow in these measurements

In the early days of transistor logic NPN transistors were used and it
was easier to design when the logic levels were 0 and -12V. With the
advent of integrated circuits it was more convenient to make the logic
levels 0 and +5V or now 0 and +3V

I had an engineer that worked for me and always drew his diodes
backwards because he had learned electron flow in the military and
never was able to completely switch his brain to conventional current
flow.

Dan

5. ### Lost'n FoundGuest

Forget the word ground, and use the word reference- referenced to zero
volts.
Electrons do flow from negative to positive. Current goes from positive to
negative. Why? Blame the man on the \$100 bill!

The way you did ur analysis before, instead of say having a battery of 12-0,
you have battery of 0- -12v, according to the universal convention. The
potential difference is still the same though.

solve some ciruits, you'll get used to it.

6. ### DanielGuest

What you mean to say is "Conventional Current flow is positive to
negative...."
When I did my basic electronics training, "Electron Current Flow" was
the method used, except for about two minute mention of Conventional
current flow!

Electrons actually
Big call, Geoff, to forget Electron Current flow.
Daniel

7. ### Don KellyGuest

However, except in some grade schools and a few tech institutes ,
conventional flow is used. Definitely so at the university level in both
engineering and physics. Actually, it really doesn't matter for solution
purposes, which way the current flows. Sometimes you don't actually know
until the math is worked out and if wrong the sign will indicate it.
Consistency is the main thing and conventional current is more consistent
overall particularly mathematically. Don't sweat it.

8. ### DanielGuest

Why would you want me to mentally rotate all the arrows? The arrows
always pointed to the N type material, so you knew how to set up your
supplies!

Perhaps the problem here is that I'm talking actual circuit operation
where as you seem to be talking circuit analysis, Thevans, Norton, that
type of stuff.
Daniel

9. ### Don KellyGuest

----------------------------
Unimportant for actual circuit operation. One doesn't count electrons or
really care about what the charge carriers actually are except in terms of
the internal design of transistors,etc. Otherwise you measure voltages and
currents (and an ammeter is scaled and marked in terms of conventional
current). However, what is the electron flow for AC?-they just wiggle
about. Pick a convention and stick with it. Note that the conventional
current is used by far more people than "electron flow" and is the standard
in both physics and engineering use. You got stuck with a tech school of
the '40's definition where all electronic devices depended on electron flow
so somebody decided to reverse the "direction" of current (causing all kinds
of future and unnecessary problems). --

Don Kelly

10. ### Ernie WerbelGuest

Ok so if I understand correctly all this it's not the way the electronic go
that's important it's the voltage potentials? So -12V to zero is the same
as zero to +12V?

But then why do you need ground? It's justa voltage reference, right? Or
does it serve some other purpose as a convenient connection point (less
wires if they go to the chassis)?