Ernie Werbel wrote:
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

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