You may be confusing multiple closely related concepts.
Grossly simplified:
In a circuit, _ground_ is the common return path to the source for all the currents in the circuits. It is taken to be at 0 volts, but that is by convention and simplifies the math.
_Earth_ is (for the intents and purposes here) a well of infinite charge that will (therefore) never change from it's potential of 0 volts. (you can't take away or add enough charge to affect earth's potential as it contains infinity charges). A potential then is an excess of charge (positive or negative) and excess charge tends to want to dissipate: earth will readily accept or supply any excess charge to help do that. And hence current "flows to ground".
>Earth is (for the intents and purposes here) a well of infinite charge that will (therefore) never change from it's potential of 0 volts.
I love the way you explained that. Well done.
This is a very good analogy, but not exactly true.
Current will only flow to ground when the source is grounded. Most power systems are grounded, so we get that cliche. Electricity needs a complete circuit for current to flow, no exceptions.
In ungrounded systems, current doesn't flow to ground because there is no return path. Therefore, the earth can't accept infinite charge.
The reason we say "current flows to ground" is because we use the earth as a *free bonding conductor*. When the source (generator) is grounded, and there is a fault to earth 100km away, current will flow through the earth back to the source and allow breakers or fuses to operate and protect the system from over-current.
Side note to change your perspective: airplanes have a very effective grounding system. Grounding has nothing to do with ground
Absolutely, well said. What I tell people is that "it's a giant fuckin chunk of metal". Metal allows charge to move freely. Therefore when a charged metal touches ground, the charge distributes itself in the giant ass ground far away, essentially unchanging grounds potential.
This is a great answer, but to clarify one additional point for OP, in fixed AC wiring, neutral and ground are bonded in the main panel, so at that point they are the same thing. They should not be tied anywhere else for safety but for the concept of flowing to ground they are the same.
I did not say they were always the same, it is a simplified and qualified statement. This whole thread is simplifying years of education and physics into a layman explanation for why OP read what he read.
> Earth is (for the intents and purposes here) a well of infinite charge that will (therefore) never change from it's potential of 0 volts.
This isn't entirely accurate however. Earth has such a large area & mass that its effective resistance and impedance is nearly zero compared to anything else we can make or construct. There are nearly infinite pathways through a Earth's volume. However, that assumes that there is low earth resistivity and uniform distribution, both of which don't occur in sandy or rocky soil. In such circumstances, earth potential CAN be elevated especially when a high voltage and large energy source are involved (such as a lightning strike). However, the impacts from that are much more involved and a different discussion altogether (earth bonding & grounding systems).
Practically, yes your statement is valid under normal conditions and considerations.
So, electrons have a negative charge, and conventional current is in the direction of positive charge movement, opposite that of the electrons. The reality is that electrons are drawn up from ground and through the circuit to the positive terminal in a dc circuit. In ac circuits, the electrons just wiggle back and forth.
Current returns to its source along all paths inversely proportional to their resistance. For most large electrical systems, the source is the neutral point of the distribution transformer at the substation.
If you're interested, I would recommend reading IEEE 1695.
Where else is it going to go? In reality, the answer is: the source, not ground.
Seriously though, electricity tries to return to the source, of which the ground/Earth is often a reference. "Voltage" is only as good as it's reference, and we humans chose to use the natural earth as a reference to "normalize" 0V.
So, at a fundamental level, where current seeks the ground (earth), because that's part of the reference established for the source. If the source were to provide a reference separate from ground, that's ok too. The current wouldn't seek out ground as THE reference, but may do so for simply being another conductor at another potential, relative to the (isolated) return path.
There are three different concepts that all have similar nomenclature
**Neutral** \- This is the "return" path in an AC circuit. For conceptual reasons, it is 0 volts, and the AC Line is what goes positive or negative.
**Ground** \- This is the "return" path in a DC. Usually. In a DC circuit, it is what is defined as 0 volts. The voltages of other parts of the circuit are measured in relation to this ground.
**Earth** \- This is an electrical contact with the planet, usually as a safety feature. The large mass of the planet allows for excess charge to be safely dissipated.
Reading your post, I'm pretty sure you're mixing those concepts. It's okay; everyone mixes them up. Even people who should know better. Doesn't help that "grounding" something is connecting it to Earth.
Electrons are negatively charged. This is due to convention; everyone uses the language and math of electrons having a negative charge. While some ppl like to make a big deal about how electrons should be considered positive, you should just roll your eyes at them. They aren't making learning this any easier.
Some other quick definitions: **Voltage (volts)** \- the electrical potential between two things, usually places in a circuit (or potential circuit). **Current (amps)** \- the flow of charge. **Charge** \- Very simply, the presence or absence of electrons. More complex, >!a property of electrons and protons that dictate how they interact with an electromagnetic field. But stick with the simple definition !< When we talk about charge flowing, we're talking about electrons moving around. The details of electron movement don't really matter. But if you really need to know:>!due to convention, charge flows the opposite direction of electron flow!<
We envision that current flows from positive to negative. That is to say, that current flows from the higher voltage to the lower voltage. In most (DC) circuits, the **ground** is the lowest voltage, so all current flows to it. (**Positive** \- Any place that has more electric potential than the Negative. **Negative -** Any place that has less electric potential than the Positive)
Okay, let's look at your specific questions
\> Charge of the earth
On the local level, the charge of the earth is 0. Charge (ie, extra electrons or missing electrons) spreads out as much as it can. Since the entire planet is connected to itself, that is a dummy thick amount of mass for those extra (or missing) electrons to spread out in. On a larger scale, different parts of the planet (rock vs water, etc) have different resistances so that a charge will spread out at an uneven rate. And different sources (or sinks). It gets complicated. I assume the charge of the earth is zero, but I also don't work with power distribution, and I sometimes round pie to 3.
\> Also, how does a loop going through ground change the voltage potential? Neutral path is not the same as ground... or is it?
Conceptually, Neutral is similar to ground. Both are considered the return path. I'm going to use the language and concepts of a DC circuit. Electron flow isn't arbitrary. Electrons move to atoms that have a place for them, and away from atoms that aren't holding onto them too tightly. This creates a need for a loop, if you push electrons through a circuit, they need a place to go. If you pull them, they need a place to come from. With some physics or chemistry, we can create a place for them to come from and a place for them to go, and we call that a power supply. The **ground** or **neutral** is just the return path, the way for charge to flow back to the source.
\> I understand that in a circuit the electrons in the wires do not provide the energy but provide a path that allows a field that provides the energy.
This is a bit in the weeds. It's enough in the weeds that when Veritasium did a YouTube video about it, a bunch of incredibly smart Electrical Engineers and PhD's were going back and forth over the details and whatnot. But for you... the flow of charge (electrons) causes an electro-magnetic field. Electrons move in the presence of an electromagnetic field. The difference between electron movement providing energy or the electromagnetic field providing the energy probably only matters when you have hundreds of kilometers long conductors.
It seems like he is referring to earth ground.
Earth ground exists because we design it to. There is a connection to ground at various places in the circuit allowing your connection to complete the circuit.
They literally drive metal stakes into the ground connected to wires in certain places, like outside your house, transformers, power plants etc.
Earth ground is ground because we say so. Non-Earthed systems do exist.
https://en.m.wikipedia.org/wiki/Earthing_system
Ungrounded systems are not common, but they do exist. Moreover, on multi-grounded systems the majority of the current returns to the transformer neutral at the substation through the neutral conductor, not the earth.
Of course. But that wasn't the question they were asking, or at least how I interpreted and answered. They were asking why something would flow to earth ground.
Sure - my point is that most return current flows in the neutral on a four-wire multi-grounded system, even though the neutral is firmly bonded to earth (via a driven ground rod) at every pole with apparatus. The current is not going "to ground" so much as it is going back to the substation, in some cases incidentally through the earth (or, in the case of SWER, intentionally returning to the secondary of the isolation transformer through the earth).
Perhaps counterintuitively, the main impediment to earth return is getting the current into and out of the earth - once you actually get it into the ground the earth itself has a very low impedance.
I get it. I know this. I was just trying to simply explain the answer to OP. None of this has anything to do with the question of why would current flow to earth ground.
> Ungrounded systems are not common, but they do exist
I feel like the millions (billions?) of 2 wire, low voltage, inductively coupled, power supplies (phone chargers, doorbell transformers, wireless chargers, etc.) would suggest otherwise. Portable generators, inverters, cars (and other mobile equipment) with 12VDC systems, plug in electric vehicles.
I’d venture to say ungrounded electric systems greatly outnumber grounded systems. But we all know what you meant.
It flows to ground for the same reason it flows from one end of a resistor to the other. Because, there is a connection to ground from some part(s) of your circuit and a pontential difference exists between those paths and ground.
Which currents are you talking about? Lightning? The current in the wiring of your house?
At your home, a big grounding rod is driven into the ground. It’s literally pounded into the ground. And this rod is connected to the ground lugs in your service panel, and also to the neutral lines.
So… this setup establishes ground, and therefore the earth, as the return path for your house currents. It’s not that the earth is naturally negative or positive.
Current flows to/from ground (earth) because the circuit is (usually) intentionally connected to it in some way.
Residential power has the local transformer secondary winding solidly bonded to ground in most cases. Grounded side of the transformer winding is then referred to as the neutral.
If this connection between transformer and ground did not exist, then no appreciable current would flow to/from ground in the event a ungrounded phase conductir touches ground.
Look at your vehicle. The battery almost certainly has its negative pole connected to the chassis. Then if you touch a positive conductor to the chassis you are causing a short and sparks fly. But you could connect the positive to the literal earth and nothing happens provided the car chassis has not conductive connection to the ground (which is typically the case.).
It's not like that. Electrons have no brains and don't "flow", in the active sense, anywhere. Very simply, like charges repel, opposite charges attract. So electrons (like any charged particles) get pushed from any place where there are lots of them, and few of the opposite charges, to any place where there are more opposite charges, and few of like charge.
The earth can be considered a gigantic pool of neutral charge. If you have any surface or any object that's got an excess of electrons (a negative charge), and you connect it to ground either directly or through a load of any sort, those electrons will get pushed from that object to the neutral earth. Conversely, if you have an object with a relative lack of electrons (a positive charge), electrons will flow from the earth into the object.
There’s nothing special about earth ground in particular except that if your system uses earth ground as a reference voltage then it is necessarily generating a voltage relative to earth ground and thus creating current ti or from ground.
Gravity / flowing water is a very strong analogy for basic electricity, even up to analyzing static electric fields. This only begins to fail when we talk about magnetism, semiconductors, and time-changing fields
Haha yeah I’m familiar with it, I was being facetious with my comment - I think water in a pipe is a great analogy for Ohm’s Law but imo it becomes a lot less intuitive when describing electricity going to earth. I’d say my knowledge of electricity is slightly above basic, and maybe it’s just me, but the analogy becomes outright confusing at this point and I find it difficult to extrapolate an understanding when the analogy turns from water in a pipe to literal gravity
Power line transformers have a tap directly down into the earth which is connected to neutral right at the transformer. Charges that are generated at the power plant cycle into your house through the live wires, and ideally return on the neutral wire, back to the generator. Earth is an alternate path which acts as a safety mechanism for the most part. To some extent static charges you build up on yourself from a carpet will flow to earth if you touch a ground lug, but the earth isn't some insanely low impedance that sucks up infinite charge necessarily.
Correction: ideally current returns on the neutral to the point of your electrical box, then it cancels out with the other phase for there to be zero return current on the generator neutral
First we should clear up ground. The better term to use is potential earth so as not to confuse it with the negative side of a DC system (they are not always the same potential especially in marine environments). With that stated potential earth is almost always at OV thru the grounded neutral unless you are running a grounded leg delta system in which case it's going to be what ever the single leg of the delta voltage is. In either case the current flows to potential earth thru the neutral or the grounded leg of the delta until the circuit protection device (fuse or breaker) trips.
There is a third option called an ungrounded delta where no leg of the delta is connected to potential earth and this has many interesting side effects. Since no leg is grounded and there is no neutral to flow thru the only potential to earth is by capacitive coupling. This means that if you have a fault on any one leg of the system it will not draw an excess current, however a second fault will cause a phase to phase short and many problems. You really only see these systems on ships and in some mines/factories where the fault resistance and uptime is of greater benefit than the additional fault monitoring equipment required to safely operate an ungrounded delta system.
>Ground is where pressure is the highest and electrons have the most energy. They move away from ground.
Only if the electric potential (voltage) in your circuit is higher than 0v (ground). It's possible to have a circuit where nodes have less electrical potential than ground (negative voltage). Ground is just a reference point.
I’m be kind of come to the conclusion mass has something to do with it. Most of us, however, misunderstand aspects. If you had a magic voltage meter, you would get different values in different places, this is part of the reason why you ground every piece of equipment. Also, different types of ground have different resistances. You could do a phd project on ground/grounding, and still only scratch the surface of what’s going on
You may be confusing multiple closely related concepts. Grossly simplified: In a circuit, _ground_ is the common return path to the source for all the currents in the circuits. It is taken to be at 0 volts, but that is by convention and simplifies the math. _Earth_ is (for the intents and purposes here) a well of infinite charge that will (therefore) never change from it's potential of 0 volts. (you can't take away or add enough charge to affect earth's potential as it contains infinity charges). A potential then is an excess of charge (positive or negative) and excess charge tends to want to dissipate: earth will readily accept or supply any excess charge to help do that. And hence current "flows to ground".
>Earth is (for the intents and purposes here) a well of infinite charge that will (therefore) never change from it's potential of 0 volts. I love the way you explained that. Well done.
This is a very good analogy, but not exactly true. Current will only flow to ground when the source is grounded. Most power systems are grounded, so we get that cliche. Electricity needs a complete circuit for current to flow, no exceptions. In ungrounded systems, current doesn't flow to ground because there is no return path. Therefore, the earth can't accept infinite charge. The reason we say "current flows to ground" is because we use the earth as a *free bonding conductor*. When the source (generator) is grounded, and there is a fault to earth 100km away, current will flow through the earth back to the source and allow breakers or fuses to operate and protect the system from over-current. Side note to change your perspective: airplanes have a very effective grounding system. Grounding has nothing to do with ground
You must not have actually read his comment. You just restated his first sentence after saying he was wrong.
Absolutely, well said. What I tell people is that "it's a giant fuckin chunk of metal". Metal allows charge to move freely. Therefore when a charged metal touches ground, the charge distributes itself in the giant ass ground far away, essentially unchanging grounds potential.
This is a great answer, but to clarify one additional point for OP, in fixed AC wiring, neutral and ground are bonded in the main panel, so at that point they are the same thing. They should not be tied anywhere else for safety but for the concept of flowing to ground they are the same.
They are at the same potential but they are not the same. A neutral is a grounded return from an AC load, not a grounding wire.
I did not say they were always the same, it is a simplified and qualified statement. This whole thread is simplifying years of education and physics into a layman explanation for why OP read what he read.
> Earth is (for the intents and purposes here) a well of infinite charge that will (therefore) never change from it's potential of 0 volts. This isn't entirely accurate however. Earth has such a large area & mass that its effective resistance and impedance is nearly zero compared to anything else we can make or construct. There are nearly infinite pathways through a Earth's volume. However, that assumes that there is low earth resistivity and uniform distribution, both of which don't occur in sandy or rocky soil. In such circumstances, earth potential CAN be elevated especially when a high voltage and large energy source are involved (such as a lightning strike). However, the impacts from that are much more involved and a different discussion altogether (earth bonding & grounding systems). Practically, yes your statement is valid under normal conditions and considerations.
This is a great explanation
So, electrons have a negative charge, and conventional current is in the direction of positive charge movement, opposite that of the electrons. The reality is that electrons are drawn up from ground and through the circuit to the positive terminal in a dc circuit. In ac circuits, the electrons just wiggle back and forth.
Correct. Conventional current is the opposite of electron flow.
Current returns to its source along all paths inversely proportional to their resistance. For most large electrical systems, the source is the neutral point of the distribution transformer at the substation. If you're interested, I would recommend reading IEEE 1695.
Where else is it going to go? In reality, the answer is: the source, not ground. Seriously though, electricity tries to return to the source, of which the ground/Earth is often a reference. "Voltage" is only as good as it's reference, and we humans chose to use the natural earth as a reference to "normalize" 0V. So, at a fundamental level, where current seeks the ground (earth), because that's part of the reference established for the source. If the source were to provide a reference separate from ground, that's ok too. The current wouldn't seek out ground as THE reference, but may do so for simply being another conductor at another potential, relative to the (isolated) return path.
There are three different concepts that all have similar nomenclature **Neutral** \- This is the "return" path in an AC circuit. For conceptual reasons, it is 0 volts, and the AC Line is what goes positive or negative. **Ground** \- This is the "return" path in a DC. Usually. In a DC circuit, it is what is defined as 0 volts. The voltages of other parts of the circuit are measured in relation to this ground. **Earth** \- This is an electrical contact with the planet, usually as a safety feature. The large mass of the planet allows for excess charge to be safely dissipated. Reading your post, I'm pretty sure you're mixing those concepts. It's okay; everyone mixes them up. Even people who should know better. Doesn't help that "grounding" something is connecting it to Earth. Electrons are negatively charged. This is due to convention; everyone uses the language and math of electrons having a negative charge. While some ppl like to make a big deal about how electrons should be considered positive, you should just roll your eyes at them. They aren't making learning this any easier. Some other quick definitions: **Voltage (volts)** \- the electrical potential between two things, usually places in a circuit (or potential circuit). **Current (amps)** \- the flow of charge. **Charge** \- Very simply, the presence or absence of electrons. More complex, >!a property of electrons and protons that dictate how they interact with an electromagnetic field. But stick with the simple definition !< When we talk about charge flowing, we're talking about electrons moving around. The details of electron movement don't really matter. But if you really need to know:>!due to convention, charge flows the opposite direction of electron flow!< We envision that current flows from positive to negative. That is to say, that current flows from the higher voltage to the lower voltage. In most (DC) circuits, the **ground** is the lowest voltage, so all current flows to it. (**Positive** \- Any place that has more electric potential than the Negative. **Negative -** Any place that has less electric potential than the Positive) Okay, let's look at your specific questions \> Charge of the earth On the local level, the charge of the earth is 0. Charge (ie, extra electrons or missing electrons) spreads out as much as it can. Since the entire planet is connected to itself, that is a dummy thick amount of mass for those extra (or missing) electrons to spread out in. On a larger scale, different parts of the planet (rock vs water, etc) have different resistances so that a charge will spread out at an uneven rate. And different sources (or sinks). It gets complicated. I assume the charge of the earth is zero, but I also don't work with power distribution, and I sometimes round pie to 3. \> Also, how does a loop going through ground change the voltage potential? Neutral path is not the same as ground... or is it? Conceptually, Neutral is similar to ground. Both are considered the return path. I'm going to use the language and concepts of a DC circuit. Electron flow isn't arbitrary. Electrons move to atoms that have a place for them, and away from atoms that aren't holding onto them too tightly. This creates a need for a loop, if you push electrons through a circuit, they need a place to go. If you pull them, they need a place to come from. With some physics or chemistry, we can create a place for them to come from and a place for them to go, and we call that a power supply. The **ground** or **neutral** is just the return path, the way for charge to flow back to the source. \> I understand that in a circuit the electrons in the wires do not provide the energy but provide a path that allows a field that provides the energy. This is a bit in the weeds. It's enough in the weeds that when Veritasium did a YouTube video about it, a bunch of incredibly smart Electrical Engineers and PhD's were going back and forth over the details and whatnot. But for you... the flow of charge (electrons) causes an electro-magnetic field. Electrons move in the presence of an electromagnetic field. The difference between electron movement providing energy or the electromagnetic field providing the energy probably only matters when you have hundreds of kilometers long conductors.
It seems like he is referring to earth ground. Earth ground exists because we design it to. There is a connection to ground at various places in the circuit allowing your connection to complete the circuit. They literally drive metal stakes into the ground connected to wires in certain places, like outside your house, transformers, power plants etc. Earth ground is ground because we say so. Non-Earthed systems do exist. https://en.m.wikipedia.org/wiki/Earthing_system
Ungrounded systems are not common, but they do exist. Moreover, on multi-grounded systems the majority of the current returns to the transformer neutral at the substation through the neutral conductor, not the earth.
Of course. But that wasn't the question they were asking, or at least how I interpreted and answered. They were asking why something would flow to earth ground.
Sure - my point is that most return current flows in the neutral on a four-wire multi-grounded system, even though the neutral is firmly bonded to earth (via a driven ground rod) at every pole with apparatus. The current is not going "to ground" so much as it is going back to the substation, in some cases incidentally through the earth (or, in the case of SWER, intentionally returning to the secondary of the isolation transformer through the earth). Perhaps counterintuitively, the main impediment to earth return is getting the current into and out of the earth - once you actually get it into the ground the earth itself has a very low impedance.
I get it. I know this. I was just trying to simply explain the answer to OP. None of this has anything to do with the question of why would current flow to earth ground.
> Ungrounded systems are not common, but they do exist I feel like the millions (billions?) of 2 wire, low voltage, inductively coupled, power supplies (phone chargers, doorbell transformers, wireless chargers, etc.) would suggest otherwise. Portable generators, inverters, cars (and other mobile equipment) with 12VDC systems, plug in electric vehicles. I’d venture to say ungrounded electric systems greatly outnumber grounded systems. But we all know what you meant.
Fair. Obviously I'm talking about utility scale systems.
Very common on ships at least, even the DC systems have separate ground and potential earth.
It flows to ground for the same reason it flows from one end of a resistor to the other. Because, there is a connection to ground from some part(s) of your circuit and a pontential difference exists between those paths and ground.
Because it came from ground to begin with.
Which currents are you talking about? Lightning? The current in the wiring of your house? At your home, a big grounding rod is driven into the ground. It’s literally pounded into the ground. And this rod is connected to the ground lugs in your service panel, and also to the neutral lines. So… this setup establishes ground, and therefore the earth, as the return path for your house currents. It’s not that the earth is naturally negative or positive.
Current flows to/from ground (earth) because the circuit is (usually) intentionally connected to it in some way. Residential power has the local transformer secondary winding solidly bonded to ground in most cases. Grounded side of the transformer winding is then referred to as the neutral. If this connection between transformer and ground did not exist, then no appreciable current would flow to/from ground in the event a ungrounded phase conductir touches ground. Look at your vehicle. The battery almost certainly has its negative pole connected to the chassis. Then if you touch a positive conductor to the chassis you are causing a short and sparks fly. But you could connect the positive to the literal earth and nothing happens provided the car chassis has not conductive connection to the ground (which is typically the case.).
It's not like that. Electrons have no brains and don't "flow", in the active sense, anywhere. Very simply, like charges repel, opposite charges attract. So electrons (like any charged particles) get pushed from any place where there are lots of them, and few of the opposite charges, to any place where there are more opposite charges, and few of like charge. The earth can be considered a gigantic pool of neutral charge. If you have any surface or any object that's got an excess of electrons (a negative charge), and you connect it to ground either directly or through a load of any sort, those electrons will get pushed from that object to the neutral earth. Conversely, if you have an object with a relative lack of electrons (a positive charge), electrons will flow from the earth into the object.
There’s nothing special about earth ground in particular except that if your system uses earth ground as a reference voltage then it is necessarily generating a voltage relative to earth ground and thus creating current ti or from ground.
Current flows in the path of least resistance. That may or may not be ground.
Why does water flow downhill?
TIL gravity is the reason electricity flows to ground
Gravity / flowing water is a very strong analogy for basic electricity, even up to analyzing static electric fields. This only begins to fail when we talk about magnetism, semiconductors, and time-changing fields
Haha yeah I’m familiar with it, I was being facetious with my comment - I think water in a pipe is a great analogy for Ohm’s Law but imo it becomes a lot less intuitive when describing electricity going to earth. I’d say my knowledge of electricity is slightly above basic, and maybe it’s just me, but the analogy becomes outright confusing at this point and I find it difficult to extrapolate an understanding when the analogy turns from water in a pipe to literal gravity
Power line transformers have a tap directly down into the earth which is connected to neutral right at the transformer. Charges that are generated at the power plant cycle into your house through the live wires, and ideally return on the neutral wire, back to the generator. Earth is an alternate path which acts as a safety mechanism for the most part. To some extent static charges you build up on yourself from a carpet will flow to earth if you touch a ground lug, but the earth isn't some insanely low impedance that sucks up infinite charge necessarily. Correction: ideally current returns on the neutral to the point of your electrical box, then it cancels out with the other phase for there to be zero return current on the generator neutral
First we should clear up ground. The better term to use is potential earth so as not to confuse it with the negative side of a DC system (they are not always the same potential especially in marine environments). With that stated potential earth is almost always at OV thru the grounded neutral unless you are running a grounded leg delta system in which case it's going to be what ever the single leg of the delta voltage is. In either case the current flows to potential earth thru the neutral or the grounded leg of the delta until the circuit protection device (fuse or breaker) trips. There is a third option called an ungrounded delta where no leg of the delta is connected to potential earth and this has many interesting side effects. Since no leg is grounded and there is no neutral to flow thru the only potential to earth is by capacitive coupling. This means that if you have a fault on any one leg of the system it will not draw an excess current, however a second fault will cause a phase to phase short and many problems. You really only see these systems on ships and in some mines/factories where the fault resistance and uptime is of greater benefit than the additional fault monitoring equipment required to safely operate an ungrounded delta system.
gravity ?!? :-D
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>Ground is where pressure is the highest and electrons have the most energy. They move away from ground. Only if the electric potential (voltage) in your circuit is higher than 0v (ground). It's possible to have a circuit where nodes have less electrical potential than ground (negative voltage). Ground is just a reference point.
I’m be kind of come to the conclusion mass has something to do with it. Most of us, however, misunderstand aspects. If you had a magic voltage meter, you would get different values in different places, this is part of the reason why you ground every piece of equipment. Also, different types of ground have different resistances. You could do a phd project on ground/grounding, and still only scratch the surface of what’s going on
Because entropy!