Why are "ground" and "(-)" often referred to as the same thing.

Ok, so, I am very confused with wire colors, ground and (+) and (-). I NEEd someone to answer me.
What I have read is that electricity flows from (-) to (+). However red wire is always connected to (+) and referred to as the "hot or "live" wire, and (-) is the ground.
This seems backwards to me.

Ground wires go to ground because it is highly positively charged,

It just seems like there is contradictions. I really need this cleared up. Thanks in advance!

kelseymh12 months ago
The ground is not "highly positively charged." Rather, true ground (i.e., the earth, soil/rock/etc.) has an extremely large capacity to absorb charge -- the number of charges flowing into the ground is tiny compared to the number of atoms present.

The confusion you feel about the signs applied to electrical circuits is due to an historical accident. There is no contradiction, just a lack of complete knowledge on your part.

When Franklin discovered that electrical current was due to flowing charges (i.e., that static and dynamic electricity were the same underlying phenomenon), there was no way do determine the absolute sign of the charge being carried, nor could he measure the direction of flow, since the speed was too high. He arbitrarily assigned positive to one end of his apparatus, and negative to the other.

When Thompson discovered the "cathode ray" (electron) 100 years later, he could use Maxwell's equations to figure out the sign of the moving charge based on how his beam was bent by a magnetic field. That sign turned out to be negative. Oops.

So, the free electrons flow from the negatively labeled side of a current source, through the circuit, and back around to the positively labeled side. However, by convention, the same convention used since the 1800's, the electric current flows from (+) to (-).

Since all electrical devices follow that convention, you should follow it as well, whether you like it or not. Wiring things up backward can mean short circuits, or the build-up of a high voltage on parts exposed to humans (like the metal shell of a project box), or frying components (like diodes) which are labelled to have the current flowing in the conventional direction.
Ampix0 (author)  kelseymh12 months ago
So if I understand you correctly, I should pretend electricity flows from (+) to (-). And everything is actually designed backwards.
kelseymh Ampix012 months ago
Its not designed "backwards," since no purely electrical system actually cares whether the charge carriers are multiples of +1.6e-19 coulombs or multiples of -1.6e-19 coulombs. A cathode-ray tube cares, a vacuum tube or photomultiplier tube cares, and components which make use of the Hall effect care. That's it.

For an electrical circuit, the "+" and "-" are arbitrary symbols without mathematical meaning. You could just as well label everything with "b" and "d", or "^" and "v", or any other pair of "opposite-looking" marks. As long as you learn and follow the same conventions everyone else follows, you won't get into trouble. If you persist in believing everything is wrong, eventually you're going to make a mistake and hurt either your equipment, yourself, or somebody else.
Ampix0 (author)  kelseymh12 months ago
I am not trying to believe everything is wrong I am obviously just not understanding. So I know electricity moves from point A to point B and as long as it goes in a loop we have a circuit. Right (legitimate question)?

What I am failing to understand is, if we were to say.. look at an arduino. You can connect to a 5v pin and end at the "ground" pin. This to me seems like power comes out of the 5v pin and flows to ground, like water in a pipe. NOW I MAY BE WRONG, I am trying to understand.

I would use a red wire on the 5v line and black on the ground. 5v is (+) and ground is (-). This is where I am confused. That looks backwards to me, because I am reading electrons move from (-) to (+).

Forgive me for not understanding.
kelseymh Ampix012 months ago
You wrote, "So I know electricity moves from point A to point B and as long as it goes in a loop we have a circuit. Right (legitimate question)?" Yes, that's exactly right.

You wrote, "What I am failing to understand is, if we were to say.. look at an arduino. You can connect to a 5v pin and end at the "ground" pin. This to me seems like power comes out of the 5v pin and flows to ground, like water in a pipe." Yes, that's correct. For a simple DC system, the flow of electricity is analogous to the flow of water through a system of pipes.

Finally, you write, "That looks backwards to me, because I am reading electrons move from (-) to (+)." Ah, ha! What you are reading is correct, and I think maybe I can help clarify things.

The movement of individual electrons in a wire is opposite the flow of current.

The electrons in a metal wire are not the electric current. Metal is a dense lattice of atoms, with offsets and other kinds of defects in that lattice structure. An individual "conduction electron" moves very, very slowly, bouncing from one atom (or lattice defect) to another. That electron drifts generally in the direction away from the "(-)" end of the circuit to the "(+)" end, but also bounce around sideways, in a more-or-less random walk.

A typical drift velocity for electrons in a metal is less than 1 mm/s. But "electricity" itself, the flow of current, moves at the speed of light (300,000 m/s)! How can that be, you ask?

Well, one way to think about it is to consider a line of dominos. Suppose you push on the first domino in a long chain. That one domino moves pretty slowly (you just barely tap it), and it doesn't move hardly at all away from where it was standing up. But the disturbance, the really cool "edge" where a tipped domino leans up against a standing one, zips along really quickly until the whole pattern has fallen down.

The metal wire is already all filled up with conduction electrons, jiggling around in a small region near whatever atom they "originally" belonged to (that way, every little piece of the wire everywhere has zero net charge). When you apply a voltage to the wire (connect one end to + and one end to -) that whole massive sea of electrons "sloshes". The individual electrons don't move very far, or very fast, but they all move together, with some (just a few) new electrons dribbling into the wire at the (-) end, and some plopping out of the wire at the (+) end. It is that collective motion we call the current.
Ampix0 (author)  kelseymh12 months ago
This clears up so much for me, I can finally start looking into this the right way. BTW, if it is alright with you, I would like to site you in the youtube video I am making (which is why I am researching this). So I think I really only have 2 more questions until I am really ready to move on.

1. Now that I understand the flow of the electrons is NOT electricity, what is really happening when you ground something, are electrons flowing up from the ground into the (+)? Which would create a current downward.

2. What exactly would you describe electricity as than. Contrary to what I though, it is not actually something flowing like water, it is a little more complicated than that, it is basically the opposite. Would it be fair to say we are harnessing the energy this movement creates (which is passed along in the opposite direction)?

Again I would like to thank you so much for helping me to understand. It finally clicked and I am starting to get it now.
kelseymh Ampix012 months ago
1) Yes. If you really ground something to earth, for example, by pounding a sharp stake into the ground and connect the "ground lug" on your generator to that stake, then some electrons will move up onto the ground connection, and some will come off the other end of that connection into your circuit.

Most electronics is not really grounded in that way. Instead, the circuit is a closed loop from a current source (+) to a current sink (-), in the form of an electrochemical potential difference (i.e., a battery). The electrons which leave the (-) end leave behind positively charged ions. Those ions get neutralized by other electrons which enter at the (+) terminal.

2. Yes. Electricity is the transfer of energy due to the movement or separation of electric charges. Those charges could be "free electrons", as in a metal wire, but they could just as easily be positively charged ions, or positively charged "holes" (vacancies in a structure). Positive charge carriers do move in the same direction as the classical current.

You are most welcome! If you want to really have your mind blown, consider that for a simple wire (a hypothetical perfect conductor), there is zero electrical energy flowing inside the wire: all of the energy is carried in the electromagnetic field which surrounds the wire. Reality is never as simple as our models, metaphors, and analogies would have us believe.
+1 on the electric charge movement. Far too many authorities fail to make the distinction between conduction in metals, which is largely carried by electrons... and virtually anyother system where conduction is by ions or vacancies.

Shall we discuss WHERE the energy is as a wire conducts a current....
You can see what a hard idea it was to get across. I'm sure this is due to the almost universal "water in a wire" analogy, and of course "every one knows" that "electricity is made of electrons." Sigh.
Ampix0 (author)  kelseymh12 months ago
This is what messed me up. I am doing research or a video and I'm reading and reading and I'm like... But that doesn't add up. The analogies I was reading made sense until I started looking at grounding and starting thinking about (+) (-) and then the whole system fell apart.
Yeah, its extremely tricky. Poynting vectors next ?
blkhawk kelseymh12 months ago
A man named Edward Leedskalnin had some theories regarding the movement of electrical currents. Has anyone discredited his "theories"?
kelseymh blkhawk12 months ago
That isn't our job. His job is to not discredit his own theories, by (a) publishing them in peer reviewed journals which are suitable for the topic, and (b) expanding upon the verifiability and falsifiability of his theories with specific observational or experimental predictions.

Failure to satisfy those criteria is sufficiently close to crackpottery to ensure that professionals are not going to waste their time.
Kiteman12 months ago
The polarity was decided upon as an arbitrary labelling system before electrons were discovered to be charge-carriers.

"-" and "ground" are the same thing, presumably (and I'm guessing here) because lightning was thought to flow from high charge ("+") to the ground ("-").

The system was too well established to change by the time electrons were discovered.

Get More Out of Instructables

Already have an Account?


PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format. You also have the ability to customize your PDF download.

Upgrade to Pro today!