Some additional questions I have to further understanding:
Ships don’t have ground, but why couldn’t electricity on a ship ground to the ocean the same way houses ground to the earth?
A structure will have a grounding rod dug into the earth. Does the dirt, soil, and rock composition that the structure is built on affect how willing current is to use the path?
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Electricity is motion of electrons. Electrons urge to move is a result of what’s called a Potential Difference. The source of the PD can be due to a moving magnetic field or simply an over-crowding of free electrons in one area with access to another area that has less electron density.
The reason the Earth makes such a good neutral ground is because relative to everything else it has effectively infinite room to accept electrons so there’s *almost* always a PD in Earth’s direction. Bodies of water absolutely could be used as a ground. Boats don’t use the water to ground out for engineering reasons (cost of wire, safety, increased corrosion).
Electricity is motion of electrons. Electrons urge to move is a result of what’s called a Potential Difference. The source of the PD can be due to a moving magnetic field or simply an over-crowding of free electrons in one area with access to another area that has less electron density.
The reason the Earth makes such a good neutral ground is because relative to everything else it has effectively infinite room to accept electrons so there’s *almost* always a PD in Earth’s direction. Bodies of water absolutely could be used as a ground. Boats don’t use the water to ground out for engineering reasons (cost of wire, safety, increased corrosion).
There’s nothing special about the surface of the earth as a ground. Airplane wiring, for example, has an electrical ground even though it’s flying through the air. Ground is an arbitrary reference point, but a useful one for safety.
The key idea is that electricity flows in response to *differences* in voltage between two different places. A 12-volt battery creates the same 12 volts of electrical “push” across its terminals whether it’s in contact with the ground or inside a chamber charged to high voltage.
It’s like height: if I ask you how tall you are, you give me the distance from your feet to your head. It’s the same whether you’re at sea level or on a hill. In designing a house we usually measure all heights up from the ground, taking the ground as zero elevation reference point. But one could build the same house taking measurements up from the basement or down from the top of the roof or from sea level. Won’t change the shape of the house or how much it hurts to fall off the roof.
In electricity it’s useful to define a “zero voltage” point in our circuit, so we can measure all voltages with respect to that point. This reference point is our electrical ground. It could be anywhere. But for safety, we usually measure voltage with respect to a point that people are touching or standing on: the solid earth, the metal case of the machine, or the body of a vehicle. That way we instantly know that a wire at 1000 volts with respect to that point is dangerous to anyone touching the ground,
A great demonstration of the idea that “ground is arbitrary” is workers who repair electrical lines using helicopters. They work on lines with hundreds of thousands of volts *relative to ground*, but since they’re not touching the ground, there’s no voltage difference between them and the wires they work on, so they’re fine.
There’s nothing special about the surface of the earth as a ground. Airplane wiring, for example, has an electrical ground even though it’s flying through the air. Ground is an arbitrary reference point, but a useful one for safety.
The key idea is that electricity flows in response to *differences* in voltage between two different places. A 12-volt battery creates the same 12 volts of electrical “push” across its terminals whether it’s in contact with the ground or inside a chamber charged to high voltage.
It’s like height: if I ask you how tall you are, you give me the distance from your feet to your head. It’s the same whether you’re at sea level or on a hill. In designing a house we usually measure all heights up from the ground, taking the ground as zero elevation reference point. But one could build the same house taking measurements up from the basement or down from the top of the roof or from sea level. Won’t change the shape of the house or how much it hurts to fall off the roof.
In electricity it’s useful to define a “zero voltage” point in our circuit, so we can measure all voltages with respect to that point. This reference point is our electrical ground. It could be anywhere. But for safety, we usually measure voltage with respect to a point that people are touching or standing on: the solid earth, the metal case of the machine, or the body of a vehicle. That way we instantly know that a wire at 1000 volts with respect to that point is dangerous to anyone touching the ground,
A great demonstration of the idea that “ground is arbitrary” is workers who repair electrical lines using helicopters. They work on lines with hundreds of thousands of volts *relative to ground*, but since they’re not touching the ground, there’s no voltage difference between them and the wires they work on, so they’re fine.
*A structure will have a grounding rod dug into the earth. Does the dirt, soil, and rock composition that the structure is built on affect how willing current is to use the path?*
Absolutely. Current will travel where ever it can proportionately to the resistance/impedance of the circuit. A ground in dry sand is very little ground at all, whereas a ground in wet clay would be much better.
I used to have a ball of melted sand on my desk from where a 7200 volt distribution line fell in a field of dry sugar sand. It was conductive enough to cause heat and melt the sand, but not enough to draw enough current to blow the fuse (which is why a power line on the ground should never be considered dead).
*A structure will have a grounding rod dug into the earth. Does the dirt, soil, and rock composition that the structure is built on affect how willing current is to use the path?*
Absolutely. Current will travel where ever it can proportionately to the resistance/impedance of the circuit. A ground in dry sand is very little ground at all, whereas a ground in wet clay would be much better.
I used to have a ball of melted sand on my desk from where a 7200 volt distribution line fell in a field of dry sugar sand. It was conductive enough to cause heat and melt the sand, but not enough to draw enough current to blow the fuse (which is why a power line on the ground should never be considered dead).
Electrons repel one another. If they bunch up, it’s like a tank of compressed air. Give them a way to flow out, they do (like opening the valve on the air tank). The difference between the pressure where they are bunched up and the pressure where they are going is called a potential (volts for electricity, gauge pressure in kPa or psi for air). Electrons just move from higher potential to lower like air does from high to low pressure — until it’s even on both sides (for example, the battery is drained or the air pressure inside a tank matches the air pressure outside it).
In most electrical circuits, you have a source of electrons and a place for them to go, often with a positive charge (which, when paired with the negative charge of the electron becomes neutral). However, another possibility is to simply let the electrons flow to a space where instead of pairing up with a positive charge, they can simply spread out so far apart that they barely repeal one another. That’s an electrical “ground”, and the “potential” is low — the electrons there have no pressure to move anywhere. It can literally be the ground where the electrons jump across salts, minerals, and moisture in the earth, but it could also be just a huge sheet of metal or system of pipes where the electrons have lots of space to spread out.
Electrons repel one another. If they bunch up, it’s like a tank of compressed air. Give them a way to flow out, they do (like opening the valve on the air tank). The difference between the pressure where they are bunched up and the pressure where they are going is called a potential (volts for electricity, gauge pressure in kPa or psi for air). Electrons just move from higher potential to lower like air does from high to low pressure — until it’s even on both sides (for example, the battery is drained or the air pressure inside a tank matches the air pressure outside it).
In most electrical circuits, you have a source of electrons and a place for them to go, often with a positive charge (which, when paired with the negative charge of the electron becomes neutral). However, another possibility is to simply let the electrons flow to a space where instead of pairing up with a positive charge, they can simply spread out so far apart that they barely repeal one another. That’s an electrical “ground”, and the “potential” is low — the electrons there have no pressure to move anywhere. It can literally be the ground where the electrons jump across salts, minerals, and moisture in the earth, but it could also be just a huge sheet of metal or system of pipes where the electrons have lots of space to spread out.
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