Does AC form a closed loop circuit?

[justin001]

To charge a conductor requires that the conductor must be insulated somehow from it's environment. That makes the conductor one plate of a capacitor while the other plate is the rest of the universe.
Capacitance is defined as the ratio of voltage to charge; C = Q / V.
From that comes; V = Q / C, so to get a huge voltage you need a big charge and a small capacitance.Worrying about the movement of electrons is a distraction. There is a magnetic field wrapped around every current in any wire. By itself that will radiate everywhere. But if there is an equal and opposite return current flowing in another wire, next to the first, the two opposite magnetic fields will cancel away from the two wires, which will prevent radiation. If you do not have a return wire you have an antenna that will radiate the energy instead of guiding it to the load.

Oh sorry I'm weak in this field.I'' learn the basics of capacitor and come back to you.

 

[justin001]

Going back to the original question
Yes there is such a loop.
But it doesn't usually include "ground"
Plus,
It's not a single loop but a series of closed loops like the links of a chain
each loop connecting two of the transformers in the long distribution chain between the power station and your house.

So the return current from your house doesn't go all the way back to the power plant, only to the transformer on the pole by your house.
That transformer recirculates its high side return current back to the transformer in a switchyard that feeds your neighborhood,
and so on all the way to a power plant somewhere.
Each transformer is the junction of two links.

View attachment 101238
maybe i should have drawn them linked ?
Naaahh, you get the idea, current doesn't cross the transformer core only energy does...

If there's any current flowing through "Ground" in one of those many links
it's because there's an unbalance, ie currents in the opposite sides of the link aren't equal.

When your studies take you to three phase you'll learn that the links are not simple two wire loops but have three main wires, plus another lesser wire called "Neutral" which is usually earthed by grounding rods.

I hope this oversimplification helps plant the concept. Really it's just Kirchoff.
In today's "Publish or Perish" academic environment textbook authors are forced to "elegantize" it.
Kudos to justin001 for hanging in there.Sorry if i have belabored the obvious.
Trying to
"Keep it simple."

old jim

Yeah thanks for that.To be honest I even couldn't get how 'three phase' works.It's true that academics has destroyed the world of intuitive science at least in a few countries.If I haven't studied that much 'ill science' in high school I might be able to understand the discussion going on here.It's really better to have a plain brain than a brain full of unrelated stuff that turns you in a loop from which you can't never escape.Also I still can't get how generators work.I'm confused with the "coils part" and can't even get why we use coils in generator.

 

[Salvador]

A coil is just a conductor wrapped in a loop , how else do you expect we could generate electricity ?The rotor can even be made of permanent magnets for smaller generators , because it only needs the magnetic field to be there but the generator output must have some sort of a conductor don't you think? Electricity flows in conductors and is also induced in them via changing EM fields.
Just out of curiosity , what was your idea about what lies inside a generator ?

By the way coils and conductors are among the most basic and fundamental parts of any electrical system , just think about it they are in all kinds of motors/generators, transformers, inductors, they make up all the wires running from power stations to homes , also antennas are mostly coils or pieces of wire each with a different length , like the radio you have in your house has that metal stick coming out of it.

P.S. Don't feel bad , many people can learn to wire three phase when they need to attach a motor to it but I think only a handful of them actually understand how the theory works , it's not exactly that easy it takes time and basics to understand all aspects of it.

 

[justin001]

A coil is just a conductor wrapped in a loop , how else do you expect we could generate electricity ?The rotor can even be made of permanent magnets for smaller generators , because it only needs the magnetic field to be there but the generator output must have some sort of a conductor don't you think? Electricity flows in conductors and is also induced in them via changing EM fields.
Just out of curiosity , what was your idea about what lies inside a generator ?

By the way coils and conductors are among the most basic and fundamental parts of any electrical system , just think about it they are in all kinds of motors/generators, transformers, inductors, they make up all the wires running from power stations to homes , also antennas are mostly coils or pieces of wire each with a different length , like the radio you have in your house has that metal stick coming out of it.

P.S. Don't feel bad , many people can learn to wire three phase when they need to attach a motor to it but I think only a handful of them actually understand how the theory works , it's not exactly that easy it takes time and basics to understand all aspects of it.

Yeah that's true.From the lessons I learned from high school when the picture of generator comes into my mind I get an north pole and south place resting on opposite sides with a conductor rotating by the power of water falling on the turbine. I'm really confused with the coil windings in a generator.I can't get where the coil windings are placed in a generator.Also I can't get where the induced current is generated or more precisely in which coil winding electromagnetic induction takes place.

 

[sophiecentaur]

Making connections to a rotating shaft is not convenient, especially when high power. So it is easiest to rotate a magnet (permanent or a low power electromagnet with slip rings) on a shaft and have the output coil(s) fixed. You get the required relative rotation and can shift a lot of power through static cables.

 

[Baluncore]

I'm really confused with the coil windings ...

Maybe you need to take apart an induction motor, a universal motor and a car alternator.
Get some scrap parts. That will show you how the conductor circuits and the magnetic paths are related.

 

[jim hardy]

It's true that academics has destroyed the world of intuitive science at least in a few countries.

I have respect for academics because they build on the steps made by intuitionists . Science leapfrogs ahead because of both. Asimov's "The Gods Theselves" has a digression on the subject. It takes both types.

Also I still can't get how generators work.I'm confused with the "coils part" and can't even get why we use coils in generator.

Generators and motors come down to right hand rule
when you take vectors and study cross product
generator and motor action become intuitive
though simple right hand rule will demonstrate it too.

it's the force on free charges inside the wires
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html
see the great picture at that site

well i guess those snobs don't want us using their images.in a generator the charges in the moving wire are pushed longways toward one end of the wire by the magnetic field, making voltage for some external use.
In a motor the charges are moved longways down the wire by external voltage, causing them to push sideways against the magnetic field making torque .
really it's that simple

old jim

 

[George K]

Some say that AC should form a closed loop circuit for electricity utilization but is there really an loop from the Power station(hot wire) to the Ground(neutral) and then from Ground to power station so that it forms a loop?

Don't be confused. Always there must be a closed loop for a current (DC or AC) to flow. The voltage (as provided by a voltage source) is just the "tendency" of the electrons to flow. But the electrons will never flow unless -somehow- the two poles of the voltage source form a closed loop. This will happen by connecting a load (a bulb, a motor, a heater e.t.c.) to the poles so that the electrons will be able to flow (from one pole of the other). And this the current. For example, connect one lead of a lamp to the + pole of a battery and the other lead of the lamp to the ground. Does any current flow through the lamp? No, it doesn't. (Electrons will not "come up" from the ground by themselves.) You should, also, connect the - pole of the battery to the ground in order to form a closed loop for the current to flow (assuming, ideally, that the "ground" is a very good conductor).

 

[justin001]

Don't be confused. Always there must be a closed loop for a current (DC or AC) to flow. The voltage (as provided by a voltage source) is just the "tendency" of the electrons to flow. But the electrons will never flow unless -somehow- the two poles of the voltage source form a closed loop. This will happen by connecting a load (a bulb, a motor, a heater e.t.c.) to the poles so that the electrons will be able to flow (from one pole of the other). And this the current. For example, connect one lead of a lamp to the + pole of a battery and the other lead of the lamp to the ground. Does any current flow through the lamp? No, it doesn't. (Electrons will not "come up" from the ground by themselves.) You should, also, connect the - pole of the battery to the ground in order to form a closed loop for the current to flow (assuming, ideally, that the "ground" is a very good conductor).

So do you mean to say that electrons come from the "ground" but not from the '-' pole of the battery that has excess of electrons?I thought that electrons flow from the '-' pole of the battery to the '+' pole of the battery due to the attraction of electrons towards an place where there is '+' charges.Is there a salt bridge in battery?I think the flow of electrons continue indefinitely because of the salt bridge.

I learned these concepts but not the salt bridge from this video:

 

[justin001]

I have respect for academics because they build on the steps made by intuitionists . Science leapfrogs ahead because of both. Asimov's "The Gods Theselves" has a digression on the subject. It takes both types.

Generators and motors come down to right hand rule
when you take vectors and study cross product
generator and motor action become intuitive
though simple right hand rule will demonstrate it too.

it's the force on free charges inside the wires
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html
see the great picture at that site

well i guess those snobs don't want us using their images.in a generator the charges in the moving wire are pushed longways toward one end of the wire by the magnetic field, making voltage for some external use.
In a motor the charges are moved longways down the wire by external voltage, causing them to push sideways against the magnetic field making torque .
really it's that simple

old jim

Oh sorry I couldn't get that.I couldn't see any 'coils' in this image.To be honest I couldn't get the rules but I think first I might need to know how a generator works and then it might be better to study about the rules.Is this rule found by experiments or is there any theoretical evidence for these rules?

 

[justin001]

Maybe you need to take apart an induction motor, a universal motor and a car alternator.
Get some scrap parts. That will show you how the conductor circuits and the magnetic paths are related.

Yeah that's right but at present I don't have these in my hand or at home.

 

[justin001]

Making connections to a rotating shaft is not convenient, especially when high power. So it is easiest to rotate a magnet (permanent or a low power electromagnet with slip rings) on a shaft and have the output coil(s) fixed. You get the required relative rotation and can shift a lot of power through static cables.

Could you tell where the coils are fixed?I'm confused with where the coils are placed in a generator and which part of the generator that has coils produce induced voltage?

 

[Baluncore]

You should be aware that there are pictures of motors and generators available on the web.
https://en.wikipedia.org/wiki/Universal_motor
The stator and/or armature is a magnetic material with longitudinal slots on the gap surface. Each coil is formed as a rectangle, bent and placed in two slots far apart. The parts of the coil outside the slots cross the end of the magnetic material. The magnetic material between the slots forms the poles of the magnetic field that cross the gap.

 

[justin001]

You should be aware that there are pictures of motors and generators available on the web.
https://en.wikipedia.org/wiki/Universal_motor

Sorry but those images are too complex.It might be because I haven't studied the basics of generators and motors.

 

[Baluncore]

Sorry but those images are too complex.It might be because I haven't studied the basics of generators and motors.

Then pull your finger out and go study the basics of generators and motors.

 

[justin001]

Then pull your finger out and go study the basics of generators and motors.

That's right.

 

[George K]

So do you mean to say that electrons come from the "ground" but not from the '-' pole of the battery that has excess of electrons?I thought that electrons flow from the '-' pole of the battery to the '+' pole of the battery due to the attraction of electrons towards an place where there is '+' charges.Is there a salt bridge in battery?I think the flow of electrons continue indefinitely because of the salt bridge.

I learned these concepts but not the salt bridge from this video:

No, I didn't mean that. Read my answer more carefully. I said:
"Electrons will not "come up" from the ground by themselves. You should, also, connect the - pole of the battery to the ground in order to form a closed loop for the current to flow."
In my example the + pole is connected to the one side of the load (through a wire) and the - pole to the other side of the load (through the ground). So, in this way, a closed loop between the two poles of the battery is formed and (only then) a current flows through the load.

 

[justin001]

No, I didn't mean that. Read my answer more carefully. I said:
"Electrons will not "come up" from the ground by themselves. You should, also, connect the - pole of the battery to the ground in order to form a closed loop for the current to flow."
In my example the + pole is connected to the one side of the load (through a wire) and the - pole to the other side of the load (through the ground). So, in this way, a closed loop between the two poles of the battery is formed and (only then) a current flows through the load.

Yeah that's right.I really meant to say about 'neutral' but I accidentally said it's from the 'ground' as from this post:https://www.physicsforums.com/threads/does-ac-form-a-closed-loop-circuit.872245/#post-5477351.I think now it's clear.