Does AC form a closed loop circuit?

AI Thread Summary
AC power does form a closed loop circuit, primarily utilizing three-phase systems that involve three wires oscillating with a 120-degree phase difference, eliminating the need for a return line. The current in these systems balances out, resulting in zero net current at any given time, which is a significant advantage for efficiency and material use. In an AC circuit, electrons vibrate back and forth due to alternating voltage, meaning they do not travel far but oscillate in place. The energy is transferred from the generator through the live wire to the appliance and returns via the neutral wire, maintaining a closed loop. Overall, the operation of AC involves complex interactions of voltage and current that are essential for efficient power distribution.
justin001
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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?
 
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Power from a power station to your home does indeed form a loop, but for most of the way the power is three phase, which means it uses 3 wires instead of 2:
https://en.wikipedia.org/wiki/Three-phase_electric_power

Essentially, instead of having the electricity flow out one wire and in the other (like at your house), with no phase difference, there are three wires that oscillate "in" and "out" between them with a phase difference of 120 degrees.
 
Yes there is a closed loop. No it does not go through the ground.

But power transmission is three phase, not single phase like in your house. In three phase circuits, no return line is needed.
How is that trick done? Look at the plot below. At every point in time, the three phases add up to zero, so there is nothing to return. Pretty clever trick don't you think? The advantage of no return is why they use three phase.

1024px-3_phase_AC_waveform.svg.png
 
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It isn't just one simple closed loop. There are three wires involved (ignore the ground / Earth conductor, which shouldn't be involved) and, at any time, the current flowing along anyone of the three will balanced by the current flowing in the other two. Alternatively, you can say that the Sum of the currents in the three phases is Zero. Look at the above diagram and take one point on one of the sinusoids (i.e. one time). The other two voltages at that time will add up to that value. Take the simple example of when one is at a peak of +1, the other two will be at -0.5. It works anywhere else too. (Just supplementing the comments already in that post)
That sounds needlessly complicated but the has some massive advantages with regard to the amount of copper (or other metals) needed to transfer a given amount of Power. Also, you can connect the three phases to a suitable Three Phase Induction Motor and you get a rotation with no commutator or lossy capacitors.
 
To be honest I couldn't get anyone's replies since I'm totally weak in this subject.I would just like to know in layman terms what really happens after the voltage is produced from the generator.I only know that there is three lines in a socket and one is live and one is neutral and one is ground.Does the induced voltage produced from the generator goes to the live wire?Also after switching at the generator the voltage is reversed so do we feel that the voltage comes from ground and reaches the generator even though actually the voltage comes from generator itself since the voltage is negative.Could anyone help me.
 
Let me blow your mind - in your breaker box you will find that the neutral wire is actually connected to the ground wire. And that ground wire is connected to a large pole driven into the ground somewhere in your yard.

voltage always comes from the generator. negative voltage just means electrons are going to move in opposite direction. The generator can push electrons or pull electrons.
 
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Yeah that's true.Could you help me with how the charges flow from the generator to the electrical appliance and where the charges go after passing through the electrical appliance?
 
in a generator, the voltage will be created across two poles. + and -. The electrons will flow from the - to the positive side. With AC the poles are flipping (in a way), so the electrons just "vibrate back and forth" you could say. In DC they would flow to the + side... in a battery for instance, the + ions would bond with the electrons, until it ran out of electrons on the one side so to speak, and your battery is dead.
 
elegysix said:
in a generator, the voltage will be created across two poles. + and -. The electrons will flow from the - to the positive side. With AC the poles are flipping (in a way), so the electrons just "vibrate back and forth" you could say. In DC they would flow to the + side... in a battery for instance, the + ions would bond with the electrons, until it ran out of electrons on the one side so to speak, and your battery is dead.
I could get that.Could you tell me more precisely how the electrons flow from generator to live wire and where does it(electrons) goes after it passes through the live wire?
 
  • #10
The simple explanation for beginners is that the charge in the conductor is like a railway train that stretches all around the circuit, to form a complete loop. With DC the train of charges travels continuously in one direction. With AC the train of charges moves backwards and forwards at the frequency of the AC supply. The energy that moves the train of charges is applied at the generator, then removed at the load appliance.
 
  • #11
So if you have a magnet moving near a conductor (usually gas engine turns a rotor with coils in a magnetic field in a generator), the changing magnetic flux will push the electrons around on that conductor. Those in turn push the neighboring electrons and so forth, and that is how the voltage gets from the generator to the wire in your outlet. The pushing force wants to push electrons through things like lightbulb filaments, which resist the electrons. That resistance and current combination is the power. After passing the resistor in the circuit, the electron is free to flow back around the neutral wire to the other pole. (but in AC, it's just vibrating)
 
  • #12
Baluncore said:
The simple explanation for beginners is that the charge in the conductor is like a railway train that stretches all around the circuit, to form a complete loop. With DC the train of charges travels continuously in one direction. With AC the train of charges moves backwards and forwards at the frequency of the AC supply. The energy that moves the train of charges is applied at the generator, then removed at the load appliance.
Could you tell from where and to the "charges moves backward and forward"?
 
  • #13
elegysix said:
So if you have a magnet moving near a conductor (usually gas engine turns a rotor with coils in a magnetic field in a generator), the changing magnetic flux will push the electrons around on that conductor. Those in turn push the neighboring electrons and so forth, and that is how the voltage gets from the generator to the wire in your outlet. The pushing force wants to push electrons through things like lightbulb filaments, which resist the electrons. That resistance and current combination is the power. After passing the resistor in the circuit, the electron is free to flow back around the neutral wire to the other pole. (but in AC, it's just vibrating)
Yeah this is where I'm stuck.Could you explain a little bit more about how the electrons vibrate in AC?
 
  • #14
Sure, in AC for one moment the voltage is positive and the electrons flow forward. The next moment the voltage is negative and the electrons flow backward. This happens very fast so the electrons don't actually move very far.I should say they want to push forward and back, not flow... The more flow means more current in the circuit.
 
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  • #15
elegysix said:
Sure, in AC for one moment the voltage is positive and the electrons flow forward. The next moment the voltage is negative and the electrons flow backward. This happens very fast so the electrons don't actually move very far.
You're on my track.Does the electron really move backward or do we feel that electrons move backward?I'm asking this since the voltage becomes negative it's sure that the pull of electrons comes from the ground.So does the electron really flow from ground or whether the electrons that flowed forward to the ground comes back?
 
  • #16
In an AC circuit with a generator, The pushing and pulling is done through a coil of wire, so nothing is connected to the real ground (earth) per se. They are pushed and pulled along a single loop of wire which makes the circuit. However electrons can flow to and from the real ground (earth), which is what lightning strikes are
 
  • #17
elegysix said:
In an AC circuit with a generator, The pushing and pulling is done through a coil of wire, so nothing is connected to the real ground (earth) per se. They are pushed and pulled along a single loop of wire which makes the circuit. However electrons can flow to and from the real ground (earth), which is what lightning strikes are
Does the same electrons that are pushed through the live wire are pulled from the ground?
Oh I forgot about the ground concept you've mentioned.I actually meant to say about 'neutral' wire.Sorry for that.
 
  • #18
Electrons are not pulled from the ground for typical AC circuits. It is possible to do this, but I think the answer to your question is electrons are not pulled from the ground.
 
  • #20
Yes, the same electrons get pushed and pulled back and forth. There are no other electrons available because it is a closed and isolated loop.
 
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  • #21
elegysix said:
Yes, the same electrons get pushed and pulled back and forth. There are no other electrons available because it is a closed and isolated loop.
Now I could get how charges in AC flows.I don't think asking this is a part of this question but could you tell how the current gets reversed in alternating current.Is this done by the commutator or is it done by the induced emf by Len'z law even though I couldn't understand this law till now.
 
  • #22
commutators are used to reverse current in the generator to keep generating DC (iirc), induced emf is what is going on with the rotating loop in the magnetic field. The changing magnetic flux causes positive and negative voltage which gives rise to AC.
 
  • #23
elegysix said:
commutators are used to reverse current in the generator to keep generating DC (iirc), induced emf is what is going on with the rotating loop in the magnetic field. The changing magnetic field causes positive and negative voltage which gives rise to AC.
Oh so does that mean we need a battery to get an DC from an AC so that the current always get reversed?Also doesn't the current gets reversed in AC?I still couldn't get why we reverse the current again in AC to get DC?Could you help me.
 
  • #24
So the commutator works by reversing the AC current when it goes negative/backward. Thus the circuit always is positive/forward (DC). no you don't need a battery.
 
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  • #25
elegysix said:
So the commutator works by reversing the AC current when it goes negative/backward. Thus the circuit always is positive/forward (DC).
I tried asking many sites of how a commutator reverses the direction of current but everyone said "it's hard to explain using words".Could you help me with this.
 
  • #26
so the black wire and neutral wire would be hooked up to the commutator as left side and right side. (it's a disk with two isolated sides). As the coil rotates in the generator it makes positive voltage for one half the cycle and negative voltage for the other half (in the coil). when the coil starts to make negative voltage the contacts (from the coil to commutator) on the disk switch sides so that the connection on the circuit is reversed and you have DC on the circuit side.
 
  • #27
elegysix said:
so the black wire and neutral wire would be hooked up to the commutator as left side and right side. (it's a disk with two isolated sides). As the coil rotates in the generator it makes positive voltage for one half the cycle and negative voltage for the other half (in the coil). when the coil starts to make negative voltage the contacts (from the coil to commutator) on the disk switch sides so that the connection on the circuit is reversed and you have DC on the circuit side.
Could you tell how the disk switch sides?That's where I'm stuck.
 
  • #28
there are brushes on the coil which drag along the disk. They rotate with the coil, and are set up so that when the voltage is switching the brushes are going to the other side of the disk (left to right or right to left). Like running your two fingers around the rim of a glass (on opposite sides), where two sides are isolated
 
  • #29
elegysix said:
there are brushes on the coil which drag along the disk. They rotate with the coil, and are set up so that when the voltage is switching the brushes are going to the other side of the disk (left to right or right to left). Like running your two fingers around the rim of a glass (on opposite sides), where two sides are isolated
Oh sorry but I still couldn't get it.Is there any animation that shows commutator reversing the direction of current?
 
  • #30
I couldn't find an animation but this picture shows the split disk and direction of rotation, with the connections... maybe it will help? you can imagine the disk and wire rotating, you see the brushes touch different sides as it rotates
1713_105349_0.gif
 
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  • #31
elegysix said:
I couldn't find an animation but this picture shows the split disk and direction of rotation, with the connections... maybe it will help?
1713_105349_0.gif
Could you tell why do we need a DC power supply to reverse the current?
 
  • #32
In this case it is a DC motor. In a generator, the motor would turn the coil and create DC where the power supply is.
 
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  • #33
elegysix said:
In this case it may be a DC motor. In a generator, the motor would turn the coil and create DC where the power supply is.
Oh that's where I was stuck.Thanks for that.Now I could get the concept of commutator.I thought without battery you can't reverse the current.After you told that it creates a DC power I could understand the working of commutator.In AC motor does the motion occurs due to the repelling effect of the conductor and the coil that gets rotated?Does the same happen in DC motor?
 
  • #34
AC motors have a few varieties, but essentially it boils down to the induced magnetic field interacting with a permanent magnetic field. They can repel or pull, I don't think there is a reason to prefer one over the other.
 
  • #35
elegysix said:
AC motors have a few varieties, but essentially it boils down to the induced magnetic field interacting with a permanent magnetic field. They can repel or pull, I don't think there is a reason to prefer one over the other.
Oh sorry I would like to know whether the coil rotates due to the repulsion between the permanent and induced magnetic field interacting?Also could you tell why the windings on a coil increase the magnetic field of the coil?
 
  • #36
yes the rotation is due to repulsion or pulling between the magnets. As for why the winding increase the magnetic field, i would say look up biot savart law. Basically the more electrons you have flowing in a loop, the stronger the magnetic field inside it becomes. So more windings is more magnetic field. I don't know why moving charges create magnetic fields, it's just a property.
 
  • #37
elegysix said:
yes the rotation is due to repulsion or pulling between the magnets. As for why the winding increase the magnetic field, i would say look up biot savart law. Basically the more electrons you have flowing in a loop, the stronger the magnetic field inside it becomes. So more windings is more magnetic field. I don't know why moving charges create magnetic fields, it's just a property.
I tried looking in wikipedia but couldn't get an image of the AC motor.s there any animation that shows the working of AC motor?
 
  • #38
justin001 said:
Does the same electrons that are pushed through the live wire are pulled from the ground?
Oh I forgot about the ground concept you've mentioned.I actually meant to say about 'neutral' wire.Sorry for that.

Just forget about the ground for a minute. The ground is not worth considering when you are learning the basics. The basics are that a complete path ("loop") is required for current to flow. A battery, a bulb and two wires are the simplest circuit to consider. Connect these in a loop and the bulb will light.
Also, it really doesn't help to try to include electrons in your first understanding. People had never heard of electrons (or any other particles) when all the laws that govern circuits were invented so you should really put yourself back in the 18th / 19th century first and get an understanding of what they knew and loved. What happens to electrons is very complicated and there is really not a simple model of conduction that 'explains' it well with electrons. They can be a snare and a delusion, I would say. It is my strong opinion that, until you understand something of QM, electrons will only confuse your understanding of electricity. Enthusiastic and poorly informed educationists have dictated the electron theory of electricity be taught to 'beginners' and most of them couldn't solve the simplest circuit equation and few of them realize that the electrons flow through wires at an average speed of just a few mm per second. (So that's a rant for you! :smile:)
You ask where the charges go and where they come from. If you have a bicycle chain, you don't consider where the individual links come from. You just know that, when you move the pedal, the crank moves and pulls the 'next' link towards it. A link on the wheel sprocket is pulled off the tooth and makes the sprocket rotate. Same with simple electrical conduction. One charge in one end and an equal charge out of the other because they are all linked to each other like a chain. You could think in terms of compression and tension in the links / charges.
If you want to use an Earth Return instead of a wire, the Earth just acts like the wire it replaces. Charge flows into the Earth at one end and is squeezed into the component at the other end and flow into the bulb and so on.
Forget the Earth Wire in a 13A plug. I doesn't carry any of the current unless there is a fault somewhere and then a fuse or a breaker will cut the circuit.
 
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  • #39
sophiecentaur said:
Just forget about the ground for a minute. The ground is not worth considering when you are learning the basics. The basics are that a complete path ("loop") is required for current to flow. A battery, a bulb and two wires are the simplest circuit to consider. Connect these in a loop and the bulb will light.
Also, it really doesn't help to try to include electrons in your first understanding. People had never heard of electrons (or any other particles) when all the laws that govern circuits were invented so you should really put yourself back in the 18th / 19th century first and get an understanding of what they knew and loved. What happens to electrons is very complicated and there is really not a simple model of conduction that 'explains' it well with electrons. They can be a snare and a delusion, I would say. It is my strong opinion that, until you understand something of QM, electrons will only confuse your understanding of electricity. Enthusiastic and poorly informed educationists have dictated the electron theory of electricity be taught to 'beginners' and most of them couldn't solve the simplest circuit equation and few of them realize that the electrons flow through wires at an average speed of just a few mm per second. (So that's a rant for you! :smile:)
You ask where the charges go and where they come from. If you have a bicycle chain, you don't consider where the individual links come from. You just know that, when you move the pedal, the crank moves and pulls the 'next' link towards it. A link on the wheel sprocket is pulled off the tooth and makes the sprocket rotate. Same with simple electrical conduction. One charge in one end and an equal charge out of the other because they are all linked to each other like a chain. You could think in terms of compression and tension in the links / charges.
If you want to use an Earth Return instead of a wire, the Earth just acts like the wire it replaces. Charge flows into the Earth at one end and is squeezed into the component at the other end and flow into the bulb and so on.
Forget the Earth Wire in a 13A plug. I doesn't carry any of the current unless there is a fault somewhere and then a fuse or a breaker will cut the circuit.
Yeah you're right.I think it's the wave that actually provides the energy(voltage) and not the electrons.That's another place where I'm stuck.I couldn't get why "water in the waves aren't actually flowing to the shore but it's the wave".I think this would help in understanding electricity as I've read from documents online.Could you help me.
 
  • #40
justin001 said:
why "water in the waves aren't actually flowing to the shore but it's the wave"
I guess I could ask you why you would necessarily expect the energy carried in the wave would need to relate to flow of the 'substance'? If you jiggle a string up and down, you don't let go of the string but a wave (Energy) will travel along it. Intuition can often be wrong. :smile:
PF has loads of threads about how the energy flows along a wire and they range from highly technical to simple mechanistic. It's quite valid (imo) to treat it at many levels and a high level may be quite unnecessary for some purposes. We all yield to the temptation to show and tell too much of what we know, when someone asks a PF question and the resulting overkill can put a chap right off the subject (they can get scared off and never come back with responses).
Introducing Waves into electrical power flow, assumes a changing situation - either at switch on or every cycle of AC. For DC conduction (after things have settled down, what's needed is a replenishable source of charges on one terminal (battery / solar cell / dynamo etc) and a sink for those charges at the other terminal. The charges each have to be given an amount of Energy (the Potential Difference across the terminals). You still don't actually need to be talking of electrons here and, of course, there can be some instances where the charge carriers don't happen to be negatively charged (electrons). A steady Voltage (PD) across the terminals will produce constant DC through an unchanging Resistance and supply a Power of VI to the load.
 
  • #41
justin001 said:
I tried asking many sites of how a commutator reverses the direction of ccurren...
Commutators are not used in AC generators.

The wiki article on alternators has a simple diagram and explanation showing how a magnet rotating inside a coil of wire pushes the electrons back and forth. It really is that simple.
 
  • #42
@Justin:
It strikes me that you are asking too many questions at once. Q and A will fail you here because you are darting from topic to topic. I have to ask what course, book or other source are you using, in addition to PF? There are answers to most of your questions in the Wiki pages about motors and generators. Why not try reading those pages - thoroughly and not skimming? You need a structured course of learning and even Wiki pages tend to have some structure to them.
 
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  • #43
justin001 said:
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?
Hi Justin!

The short answer is no. The current entering - and simutaneously returning from - your house only reaches the last power transformer near your house! It does not extend beyond that to the other transformers, much less the generators at a power station.On the other hand, each transformer completes a closed current loop. The power station is also part of a closed loop. Each loop is chained to the next by transformers until a load in your home is part of the last loop.

I see that you are asking for some really fundamental level of understanding. So it is important to start discussion with the basics.

With both current and voltage together, you can transport *power* and achieve *work*. You simultaneously need both current and voltage.There is no practical circuit, with current flow, unless there is a closed loop. When the loop is open, there is no current flow. For example, when you connect a single phase AC power cord to a device you are connecting at least two wires. The current on the two wires are equal but opposite. The total current (entering and leaving) adds up to zero at all times. If you disconnect one wire, either wire, the current stops. Without both current and voltage you cannot transport *power* or achieve *work*. The important feature of AC power systems is that they can use transformers to raise the voltage (and lower the current). Or vice-versa. Voltage up, current down. Current up, voltage down. A fundamental feature of transformers is that input and output can be easily isolated by design. The input current is separated from the output current. These currents are separate streams. Their waveforms may be in lockstep, but are comprised of a separate set of electrons.Single phase AC loads are supplied by just two wires. The power transformer outside a residential house is a single phase AC load using a three phase AC supply. Perhaps ony two wires of the three phase system run past the transformer.Between the transformer and your house is *another power circuit*. Treat it as if it is dependent upon but otherwise isolated from the three phase AC system. This isolation is typical of most power transformers. So the current entering - and simutaneously returning from - your house only reaches the last power transformer! If you would like, here is more complexity:Transformers work best on alternating current, AC.Circuits that provide electrical power do not need to be grounded. That is how we can utilize power on airplanes, and all portable devices *insulated* from the ground, like cars.(Grounding of massive utility power systems is done for safety purposes, not to allow utilization or generation. In most states, only one of the utility load conductors is grounded at regular intervals every 500 feet or so, just for safety. This is the *grounded conductor* AKA neutral. The highest voltage circuits, run for extreme distances, are not grounded this way. In California, by legislation, the grounded conductor is not a load conductor. This mandate increases the number of wires, used by the utility, by one.)Large power systems were designed by Nicola Tesla as *three-phase* AC. He did this so there would be continuous smooth power transmission within the period of time of one AC cycle, so that torque was an inheirent property of three windings, so transformers could be used, and the minimum of three wires could be used for long distance power transmission. With three phase AC, there are three powered currents that continuously add up to zero. This can be conducted by three wires or four, depending on design. The loads can be single phase, three phase or any mixture.Three phase loads *need all wires* to supply current (3 or 4). Disconnecting a single wire is always a Bad Thing to do, as the load is designed to require all three (or four).
 
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  • #44
patellar-myotatic said:
Hi Justin!

The short answer is no. The current entering - and simutaneously returning from - your house only reaches the last power transformer near your house! It does not extend beyond that to the other transformers, much less the generators at a power station.On the other hand, each transformer completes a closed current loop. The power station is also part of a closed loop. Each loop is chained to the next by transformers until a load in your home is part of the last loop.

I see that you are asking for some really fundamental level of understanding. So it is important to start discussion with the basics.

With both current and voltage together, you can transport *power* and achieve *work*. You simultaneously need both current and voltage.There is no practical circuit, with current flow, unless there is a closed loop. When the loop is open, there is no current flow. For example, when you connect a single phase AC power cord to a device you are connecting at least two wires. The current on the two wires are equal but opposite. The total current (entering and leaving) adds up to zero at all times. If you disconnect one wire, either wire, the current stops. Without both current and voltage you cannot transport *power* or achieve *work*. The important feature of AC power systems is that they can use transformers to raise the voltage (and lower the current). Or vice-versa. Voltage up, current down. Current up, voltage down. A fundamental feature of transformers is that input and output can be easily isolated by design. The input current is separated from the output current. These currents are separate streams. Their waveforms may be in lockstep, but are comprised of a separate set of electrons.Single phase AC loads are supplied by just two wires. The power transformer outside a residential house is a single phase AC load using a three phase AC supply. Perhaps ony two wires of the three phase system run past the transformer.Between the transformer and your house is *another power circuit*. Treat it as if it is dependent upon but otherwise isolated from the three phase AC system. This isolation is typical of most power transformers. So the current entering - and simutaneously returning from - your house only reaches the last power transformer! If you would like, here is more complexity:Transformers work best on alternating current, AC.Circuits that provide electrical power do not need to be grounded. That is how we can utilize power on airplanes, and all portable devices *insulated* from the ground, like cars.(Grounding of massive utility power systems is done for safety purposes, not to allow utilization or generation. In most states, only one of the utility load conductors is grounded at regular intervals every 500 feet or so, just for safety. This is the *grounded conductor* AKA neutral. The highest voltage circuits, run for extreme distances, are not grounded this way. In California, by legislation, the grounded conductor is not a load conductor. This mandate increases the number of wires, used by the utility, by one.)Large power systems were designed by Nicola Tesla as *three-phase* AC. He did this so there would be continuous smooth power transmission within the period of time of one AC cycle, so that torque was an inheirent property of three windings, so transformers could be used, and the minimum of three wires could be used for long distance power transmission. With three phase AC, there are three powered currents that continuously add up to zero. This can be conducted by three wires or four, depending on design. The loads can be single phase, three phase or any mixture.Three phase loads *need all wires* to supply current (3 or 4). Disconnecting a single wire is always a Bad Thing to do, as the load is designed to require all three (or four).
That's a good explanation for three phase.Also a new information about the voltages reaches the "last transformer".I'll ask questions regarding this after I learn how AC generators work.
 
  • #45
russ_watters said:
Commutators are not used in AC generators.

The wiki article on alternators has a simple diagram and explanation showing how a magnet rotating inside a coil of wire pushes the electrons back and forth. It really is that simple.
To be honest I couldn't understand it.It might be because I'm weak in this subject.
 
  • #46
sophiecentaur said:
I guess I could ask you why you would necessarily expect the energy carried in the wave would need to relate to flow of the 'substance'? If you jiggle a string up and down, you don't let go of the string but a wave (Energy) will travel along it. Intuition can often be wrong. :smile:
PF has loads of threads about how the energy flows along a wire and they range from highly technical to simple mechanistic. It's quite valid (imo) to treat it at many levels and a high level may be quite unnecessary for some purposes. We all yield to the temptation to show and tell too much of what we know, when someone asks a PF question and the resulting overkill can put a chap right off the subject (they can get scared off and never come back with responses).
Introducing Waves into electrical power flow, assumes a changing situation - either at switch on or every cycle of AC. For DC conduction (after things have settled down, what's needed is a replenishable source of charges on one terminal (battery / solar cell / dynamo etc) and a sink for those charges at the other terminal. The charges each have to be given an amount of Energy (the Potential Difference across the terminals). You still don't actually need to be talking of electrons here and, of course, there can be some instances where the charge carriers don't happen to be negatively charged (electrons). A steady Voltage (PD) across the terminals will produce constant DC through an unchanging Resistance and supply a Power of VI to the load.
I accept that for a string while for a wave I think the water at least displace a few centimeters ahead isn't it?
 
  • #47
justin001 said:
To be honest I couldn't understand it.It might be because I'm weak in this subject.

You may have more luck with this YouTube video on AC generators. Other videos show how DC generators work.

 
  • #48
justin001 said:
I accept that for a string while for a wave I think the water at least displace a few centimeters ahead isn't it?
Out in open water, the individual particles of water actually move in vertical circles: up forward down backwards. No 'flow'. In deep enough water with small amplitudes, that' the way it goes. It's linear. In a shelving beach, the waves get steeper and break but there is also an undertow so even then there's no net flow. It's a combination of transverse and longitudinal waves and not how most people describe it.
 
  • #49
sophiecentaur said:
Out in open water, the individual particles of water actually move in vertical circles: up forward down backwards. No 'flow'. In deep enough water with small amplitudes, that' the way it goes. It's linear. In a shelving beach, the waves get steeper and break but there is also an undertow so even then there's no net flow. It's a combination of transverse and longitudinal waves and not how most people describe it.
Could you tell whether undertow is a displacement of a water a few centimeters ahead?
 
  • #50
anorlunda said:
You may have more luck with this YouTube video on AC generators. Other videos show how DC generators work.


Sorry but I couldn't play that video.It might be because You Tube is blocked in our college.
 
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