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Question with myth #1 that "electricity is trying to get to ground". Would that be an accurate statement if you replaced "ground" with a place of lower electric

Question with myth #1 that "electricity is trying to get to ground". Would that be an accurate statement if you replaced "ground" with a place of lower electrical potential? Or can you elaborate but the meaning that it's trying to get back to it's source?

vvillyd 7y ago
Well, electrical potential is only defined as a relation between two points. So the neutral point on a transformer, for example, doesn't have any electrical potential in and of itself. It has electrical potential with relation to, say, the termination point of one of the phases. The electrical potential between any two given points is dependent on the impedance along the pathway between the two. The lower the impedance, the lower the potential (or work/energy needed to move current). So, yes, in a way electricity wants to get to the point with the lowest potential, but that point will always be the point where the electricity originates. I was a little vague with "where the electricity originates" because that could be a number of things. It could be a battery, a transformer, a generator, a turbine, a dynamo, etc. Whatever is creating the difference in potential between two points is the "source" of the electricity.
- throwaway542134 7y ago
  I've always preferred to think of it as pumping water from the bottom of a (practically infinite) reservoir and dumping it at the top of a mountain then doing some work as it flows downhill, back to the reservoir. It provides a nice visual for why current always makes it back to ground, just like water always flow downhill. It also removes the tendency to anthropomorphize electrical current and say things like it "seeks out" ground. When something falls from the sky we don't say it's trying to find the ground!
  - shreddish 7y ago
    Yes water is a great way to describe electricity in a lot of ways. I'm just struggling with the "returning to where it originates". For instance the electricity didn't originate from the grounding rod it came from the transformer. Earth is providing a very low electrical potential that the electricity is "attracted" to or "falling" to in the reservoir example. Am I wrong in thinking that all electricity is flowing back into earth?
    - bsder 7y ago
      > Am I wrong in thinking that all electricity is flowing back into earth? Yes, sadly, you are wrong. But it's not a strange error. Electricity always flows in a circle(circuit). And, in fact, in medical devices, transformers are often used to completely isolate devices from the line that they are plugged into. Electrons on the device side of the transformer will NOT try to flow back into the line side or an earth. They only want to flow back to the device side of the transformer. Now, the issue is that when you want to create really strict isolation like this, suddenly all manner of things that normally you don't pay attention to suddenly become relevant. Is the device side of that transformer really not connected to the line side anywhere? No goop on the board? No water vapor? No lines that are a little too close? Is the hospital bed not connected to anything? Guitar players who use tube amps and vocalists who use condenser microphones wind up with this issue all the time. Both the amps and the mics are "isolated" with relatively high voltage signals floating around--300-400V for amps:48V for mics--and consequently strange paths cause lots of "buzz" in the signal.
      - shreddish 7y ago
        Yes instinctivly it wasn't making sense as I knew the circuit needs to be "completed". So if that's the case then what is the point of the ground rod that the neutral bar/wires in your breaker box are connected to?
        NobodyNada 7y ago
        This article posted in a comment above explains it well: http://amasci.com/amateur/whygnd.html http://amasci.com/amateur/whygnd.html Essentially, the ground rod acts as an "anchor" holding the neutral wire and the ground at the same electric potential. If there was no ground rod, the earth and the circuit would be "floating" relative to one another, and a dangerously large voltage could develop between them.
      - kmill 7y ago
        When it comes to AC (even discontinuous DC), closed loops are not necessary for current flow. A basic example is a capacitor, which can permit current while it builds up an electric field between is plates. A related example is an antenna, where AC radiates energy that can vibrate electrons in a far away antenna. (Radio telescopes are proof an antenna doesn't need a ground or a closed circuit to receive.)
  - kmill 7y ago
    This analogy doesn't work so well for AC, which involves both pushing and pulling on electric charges. It's more like pipes full of a gas like air. The power plant has a big reciprocating piston that is pushing and pulling on the gas, creating a pressure wave. One side of the cylinder is "aired," meaning it is in contact with atmospheric air. These pipes make their way to clients, who attach the pipes to equipment of their own, for example a piston that converts this wave back into mechanical energy. Again, one side of this piston is in contact with atmospheric air, which is the reference pressure for the piston. Sometimes the pipe develops small holes, and if a hapless worker gets too close, they can either get cut from an out-blast or hurt from smashing against the equipment when the air is sucking in (both being from the difference in the pipe's pressure relative to atmospheric pressure). As a safety protection, everything is enclosed in another layer of air-proof material, and when a leak is detected the main air supply is shut off. Special attention is made to make sure the average pressure in the pipe is the same as atmospheric pressure, since the piston motors depend on this to function. (In real life, steam plants use direct current since there are a lot of losses due to condensation, and also since a lot of the point is transmitting thermal energy.)

vvillyd 7y ago

Well, electrical potential is only defined as a relation between two points. So the neutral point on a transformer, for example, doesn't have any electrical potential in and of itself. It has electrical potential with relation to, say, the termination point of one of the phases. The electrical potential between any two given points is dependent on the impedance along the pathway between the two. The lower the impedance, the lower the potential (or work/energy needed to move current). So, yes, in a way electricity wants to get to the point with the lowest potential, but that point will always be the point where the electricity originates. I was a little vague with "where the electricity originates" because that could be a number of things. It could be a battery, a transformer, a generator, a turbine, a dynamo, etc. Whatever is creating the difference in potential between two points is the "source" of the electricity.

throwaway542134 7y ago
I've always preferred to think of it as pumping water from the bottom of a (practically infinite) reservoir and dumping it at the top of a mountain then doing some work as it flows downhill, back to the reservoir. It provides a nice visual for why current always makes it back to ground, just like water always flow downhill. It also removes the tendency to anthropomorphize electrical current and say things like it "seeks out" ground. When something falls from the sky we don't say it's trying to find the ground!
- shreddish 7y ago
  Yes water is a great way to describe electricity in a lot of ways. I'm just struggling with the "returning to where it originates". For instance the electricity didn't originate from the grounding rod it came from the transformer. Earth is providing a very low electrical potential that the electricity is "attracted" to or "falling" to in the reservoir example. Am I wrong in thinking that all electricity is flowing back into earth?
  - bsder 7y ago
    > Am I wrong in thinking that all electricity is flowing back into earth? Yes, sadly, you are wrong. But it's not a strange error. Electricity always flows in a circle(circuit). And, in fact, in medical devices, transformers are often used to completely isolate devices from the line that they are plugged into. Electrons on the device side of the transformer will NOT try to flow back into the line side or an earth. They only want to flow back to the device side of the transformer. Now, the issue is that when you want to create really strict isolation like this, suddenly all manner of things that normally you don't pay attention to suddenly become relevant. Is the device side of that transformer really not connected to the line side anywhere? No goop on the board? No water vapor? No lines that are a little too close? Is the hospital bed not connected to anything? Guitar players who use tube amps and vocalists who use condenser microphones wind up with this issue all the time. Both the amps and the mics are "isolated" with relatively high voltage signals floating around--300-400V for amps:48V for mics--and consequently strange paths cause lots of "buzz" in the signal.
    - shreddish 7y ago
      Yes instinctivly it wasn't making sense as I knew the circuit needs to be "completed". So if that's the case then what is the point of the ground rod that the neutral bar/wires in your breaker box are connected to?
      - NobodyNada 7y ago
        This article posted in a comment above explains it well: http://amasci.com/amateur/whygnd.html http://amasci.com/amateur/whygnd.html Essentially, the ground rod acts as an "anchor" holding the neutral wire and the ground at the same electric potential. If there was no ground rod, the earth and the circuit would be "floating" relative to one another, and a dangerously large voltage could develop between them.
    - kmill 7y ago
      When it comes to AC (even discontinuous DC), closed loops are not necessary for current flow. A basic example is a capacitor, which can permit current while it builds up an electric field between is plates. A related example is an antenna, where AC radiates energy that can vibrate electrons in a far away antenna. (Radio telescopes are proof an antenna doesn't need a ground or a closed circuit to receive.)
- kmill 7y ago
  This analogy doesn't work so well for AC, which involves both pushing and pulling on electric charges. It's more like pipes full of a gas like air. The power plant has a big reciprocating piston that is pushing and pulling on the gas, creating a pressure wave. One side of the cylinder is "aired," meaning it is in contact with atmospheric air. These pipes make their way to clients, who attach the pipes to equipment of their own, for example a piston that converts this wave back into mechanical energy. Again, one side of this piston is in contact with atmospheric air, which is the reference pressure for the piston. Sometimes the pipe develops small holes, and if a hapless worker gets too close, they can either get cut from an out-blast or hurt from smashing against the equipment when the air is sucking in (both being from the difference in the pipe's pressure relative to atmospheric pressure). As a safety protection, everything is enclosed in another layer of air-proof material, and when a leak is detected the main air supply is shut off. Special attention is made to make sure the average pressure in the pipe is the same as atmospheric pressure, since the piston motors depend on this to function. (In real life, steam plants use direct current since there are a lot of losses due to condensation, and also since a lot of the point is transmitting thermal energy.)