@walt rapp posted:

The person said "Power goes out and does it's job, what needs "returned"?"

Did you ask how well the coffee maker with just one prong on the plug is working out?  Or why AA batteries have two ends instead of just one?

Like I said Rob, I KNOW that it's needed, but what purpose does it serve?  Also as I said, "completing the circuit" is not quite a good enough answer for my friend

walt

@ADCX Rob posted:

Did you ask how well the coffee maker with just one prong on the plug is working out?  Or why AA batteries have two ends instead of just one?

Or the one wire toaster………

@walt rapp posted:

My Father started allowing for me to help set up and wire the family Christmas layout when I was as young as 7.  After which he allowed me to do it on my own each year, with him available to consult with when needed.  So I'm VERY comfortable around wiring, even though I don't understand, or care to understand, underlying theories.

BUT......

Yesterday I was asked what on the surface seems like a little harmless question: what is the purpose of a return/ground wire on a layout?  Answering "To complete the circuit" was not an acceptable answer but the only one that I had.  The person said "Power goes out and does it's job, what needs "returned"?"

So, I'm asking you here: what is a SIMPLE, DOWN TO EARTH non-theoretical answer to that question.  I know it's needed but that's not the question

As always, thanks

walt

The term "ground" can mean different things. When a circuit is looked at locally, ground is simply the one net someone picked to call 0V so that all other voltages are understood to be relative to it. Voltage is after all a relative concept. There is no such thing as 20V absolute, only 20V here with respect to there. "Ground" is a handy short form for a common there so you don't have to keep saying it.

Such a ground is often chosen to be the negative supply voltage. That makes other voltages positive, which just makes things mentally easier. In general you try to chose ground as the point in the circuit signals and the like are referenced to by individual subsections. Usually there is a clear and obvious choice. Sometimes you just have to pick one.

The other "ground" refers to real earth potential, or at least the potential of the general surroundings. This matters when power and signals are coming from or going outside your little circuit. For power and saftey, you have to assume a user could be tied to this ground, and you have to make sure you don't have a dangerous potential to ground to avoid zapping someone. Earth ground can also matter for radio systems since some types of antennas actually use the earth as part of the overall antenna system.

Think of it this way. The “charge” is there but how does it decide to “flow” somewhere? It needs a place with a lower charge to flow. That place is “ground” and once ground is connected to the circuit the place of higher charge will flow the place of lower charge.

@rplst8 posted:

Think of it this way. The “charge” is there but how does it decide to “flow” somewhere? It needs a place with a lower charge to flow. That place is “ground” and once ground is connected to the circuit the place of higher charge will flow the place of lower charge.

P.S the rate at which the charge will flow depends on two things. The amount of charge, and how easy the path is to the point of lower charge.

Without ground, a place having some charge will eventually equalize with its surroundings. But it will do so slowly. A low resistance (easy) path just allows the charge to flow more quickly.

It isn't necessary to think of electrical current (electrons) as flowing back to its original location through the Earth, the ground, or a grounded rail. By connecting the return side of a circuit to a ground, you allow electrons that had been boosted to a voltage (energy state or electrical potential) greater than ground by a power source (such as a battery or transformer) to return to ground potential - the energy state where they were initially. In the process of moving through the circuit, the increased energy in the electrons may have been used to turn a motor which moves a train, and the electrical energy is converted to kinetic energy (energy of motion). After that energy transfer occurs, the energy level of the electrons returns to its initial value - the ground potential.

MELGAR

Good answers so far! Without voltage differential there is no current flow. If we apply differential voltage to the two terminals of a load, current will flow. Without a return path to the lower voltage level, there is no flow because there is no differential.

Think of it like your garden hose. Higher pressure water wants to flow towards lower pressure if it can. When you turn the tap on (aka switch) water will flow to the lower pressure (atmospheric pressure). Your lawn sprinkler can be thought of as the load. It introduces resistance to flow (small holes), which will restrict the volume of water that flows accordingly, like higher electrical resistance restricts current flow. With higher water pressure (like higher voltage) there is more water flow for a given resistance. In the garden hose case the atmosphere is the lowest energy case.

Rod

Here's a really simple way of thinking about it:  if there was no path for all the electrons to return after they've done their work, you'd get a huge pile-up of electrons in your device, whose buildup of negative charge would stop further electrons from coming in.

@walt rapp posted:

The person said "Power goes out and does it's job, what needs "returned"?"

The wires and the electrons in it do NOT get "consumed" and the electrons can only move easily if they are arranged in a closed loop.  Wire are conductors (electrons flow easily within them).  If you break the loop, the electrons will not flow easily because they must now move out of the conductor into a non-conductive (less) material.

Pull a wire from a complete curcuit where electricity is flowing and you will see a spark.  The spark is caused by the electrons moving from the conductor to the air molecules and back to the conductor on the other side.  With the spark you will also smell ozone.  That is because you have ionized the "air".  The circuit will become MORE INEFFICENT due to this gap in the conductor.  Pull them farther apart and the spark and flow will stop.  The current is insufficient to overcome this gap due to the less conductive air.

When you are buying power from the electric company you are NOT paying for consuming electrons.  You are paying for the equipment to move the electrons through the wire.  (And also the wire itself to get it to YOUR wiring).  Plus the power consumed by the generator at the power plant.  Read on.

Analogy - A loop of pipe (wire) with water in it (electrons) with 2 water wheels encased inside it on opposite sides of the loop.  One waterwheel when turned gets the water moving through the pipe (Generator).  The other wheel in turn gets moved by the flow of the water (Motor).  The more resistance on the motor shaft the harder it is to turn the generator shaft.  BTW with this analogy if the pipe breaks it no longer works because the water spills out (electrons can't complete their journey).

If your friend won't accept this explanation, I suggest you find a new friend (it's up to you).  LOL

Let's confuse him a little more and talk about lightning.

Does a source of electricity ever run out of electrons?

Walt; I bet you're sorry you asked?

@walt rapp Curious to hear your reactions to these proposals.

@walt rapp posted:

Like I said Rob, I KNOW that it's needed, but what purpose does it serve?  Also as I said, "completing the circuit" is not quite a good enough answer for my friend

Well, "completing the circuit" is just shorthand for what's actually going on. Here's my thumbnail sketch FWIW (based on early 20th century conventions, and ignoring quarks and all the fancy stuff underlying the somewhat simplified version detailed below!):

I'm going to assume your friend knows that all atoms are comprised of protons and neutrons in the nucleus, and electrons in 'shells' or levels around the outside, with protons having a positive charge, and electrons having an equal negative charge (neutrons have no charge). At rest, each atom has an equal number of protons and electrons, and thus is electrically neutral. However, electrons in the outer shell can sometimes be temporarily knocked loose by outside forces, or free electrons temporarily captured by a previously neutral atom (since each 'shell' has a preferred number of electrons, and will more easily lose or gain one or more electron to match that preference, even without a matching proton in the nucleus). Materials that can easily lose or gain electrons are called "conductors" (metals, mostly), while those that resist exchanging electrons are classified as "insulators". "Voltage" is a measure of any force encouraging the free electrons to migrate in a given direction (or for the "holes" left by loss of the electrons to migrate in the opposite direction). "Current" is a measure of the volume of flow of the free electrons in a given direction (or of the "holes" going in the opposite direction). "Resistance" is the measure of "friction" to that flow of electrons/holes through the material.

So, to get back to the friend's question: to allow the electrons to continue to flow, there must be a return path for them to follow  to get back to the power source (they can *temporarily* flow to queue up in one side of a capacitor, but eventually they will need a return path to do much of anything useful over time). It is the *flow* of those electrons that does the actual work, since power (measured in watts) equals the pressure (in volts) times the volume of flow (in amps), so if there's no flow possible because of an open circuit, there's no power being delivered to any connected part even if there's a measurable potential along the single wire from the source, unless and until a return path is provided.

Dunno if this simplified description will help or just confuse things further, but I generally find a rough-and-ready understanding of what's going at the atomic and sub-atomic level helpful in making sense of what's going on in the layout's electrical and electronic circuits . . . especially when you get into the sometimes weird semiconductor world!

I'm sure YouTube can answer your friends questions, also.

WOW!  What a GREAT set of answers!  My own understanding took a huge leap reading these answers!  Simplistic terminology just like I asked for.

My big 'learn' is that the electrons don't actually get 'consumed' by the motor in the engine.  They merely transfer their energy to it and pass back thru.  Loved reading the examples given by you guys that explained the process so clearly.

@Rod Stewart : no, i'm not at all sorry that i asked!  in contrast, I am happy that I did.  What made it a pleasant learning experience was that theory and formulas didn't get involved to complicate the discussion.

As I typically say "As always, thanks"

walt

A picture is worth a thousand words .....

Love the Illustration, Never have seen OHMS LAW explained that way.

That's a great illustration, I never saw that one either.

@gunrunnerjohn posted:

Let's confuse him a little more and talk about lightning.

Does a source of electricity ever run out of electrons?

I would have but it didn't strike me at the time.  Yuk yuk yuk yuk yuk yuk.

@MainLine Steam posted:

I would have but it didn't strike me at the time.  Yuk yuk yuk yuk yuk yuk.

Have we squeezed all the 'juice' we can out of this topic? Gotta stay 'current', after all . . .

neural/ground do not do the same thing. one returns current, the other is for safety?

@WT.Co. posted:

neural/ground do not do the same thing. one returns current, the other is for safety?

Separate ground and neutral are really just an AC power grid thing. So yes, in that context “ground” is a safety ground, in NEC parlance, the “grounding conductor”. The neutral is the “grounded conductor”.

@Steve Tyler posted:

Have we squeezed all the 'juice' we can out of this topic? Gotta stay 'current', after all . . .

Steve, I don't know Watt you're talking about!

@Richie C. posted:

A picture is worth a thousand words .....

Richie, that is a truly great picture, thanks, and I have saved it for future use with some my "charges". I have, in the past 40 years in the mechanical trades, had to explain resistance to flow many, many time. Mr. Ohm is analogous to your foot on the garden hose. I won't get into fluid viscosity, etc etc.

Walter, In reading the original question and mulling a digestible answer for your friend, try this, knowing that the flow of water, as well as the resistance to flow, and the flow of electricity have many parallels:

Have your friend open his car hood. He has a radiator with. top hose and a bottom hose. Water makes a complete  circuit all the time the engine is running. His significant other gets cold, so he turns the heat on. The heater hoses likewise have to make a complete circuit, albeit a smaller one. The heater in turn consumes a portion of the available energy imparted to the coolant by the engine.  In train parlance, that would be your locomotive. If you asked him to put a pair of vise grips on one of the two heater hoses, I'll hazard a guess he'd say "you can't do that... the flow  (heat) would stop!"  You say "BINGO! "

Electricity is the same. If you yank off the ground(or neutral) wire, the flow will stop.....

Hope this helps!

Bob

I have removed my comment as it was too serious.

Charlie

@endless tracks posted:

Steve, I don't know Watt you're talking about!

Erg . . .

@Steve Tyler posted:

Erg . . .

Someone should write a coulomb about this in the magazine.

@rplst8 posted:

Someone should write a coulomb about this in the magazine.

It would no doubt be short, and perhaps a bit shocking . . . but some would no doubt get a charge out of it! 😱

But read with frequency never hertz.....

@endless tracks posted:

But read with frequency never hertz.....

I dunno, it could meet with some resistance.....

@Rod Stewart posted:

I dunno, it could meet with some resistance.....

Ya think this inverted discussion may have exceeded its capacitance???

These electrical jokes are lame...

Don't you have any current ones?

@woodsyT posted:

These electrical jokes are lame...

Don't you have any current ones?

Oh my god, ….you’ve ground this to a pulp!….

Pat

@endless tracks posted:

Ya think this inverted discussion may have exceeded its capacitance???

I'm somewhat coil to the idea . . . I approach it with some inductance . . . ⚡️

@Steve Tyler posted:

I'm somewhat coil to the idea . . . I approach it with some inductance . . . ⚡️

While I was looking up inductance, Steve grabbed my word!! LOL

I have a neutral opinion on that, but do find the Forum a great conduit for exciting the field of comments

Did you hear about the electrician that was arrested for eating batteries?

He is supposed to be charged tomorrow morning 🤓🤔😳🤓

Ohm My God! If these puns get any worse, I'm jumping off of the Whetstone Bridge. 

@Conductor Earl posted:

Ohm My God! If these puns get any worse, I'm jumping off of the Whetstone Bridge.

Do I see a Conductor insulated in PVC jacketing??

I'm alternating between the current question and trying to be positive, not negative.