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sirsajid
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What is the difference between neutral and ground??
one more question what is the practical example of current source
one more question what is the practical example of current source
sirsajid said:What is the difference between neutral and ground??
one more question what is the practical example of current source
A voltage source in series with a resistor.sirsajid said:what is the practical example of current source
tiny-tim said:hi sirsajid! welcome to pf!
neutral is part of the circuit … touch it and you die
ground (or earth) is not part of the circuit (unless something goes wrong)
not sure what you mean by "current source"
tiny-tim said:hi sirsajid! welcome to pf!
neutral is part of the circuit … touch it and you die
gnurf said:A voltage source in series with a resistor.
psparky said:In other words...there is no such thing as a current source.
DragonPetter said:I would not go this far. When you talk about a source, usually you mean it is supplying something to a load. A voltage source is equally valid as a current source, they are a duality (for example, thevenin and norton equivalence). The difference between the two I think is more of a convention issue, as it is which is being regulated/held constant or which your load is dependent on.
You can design a source that's voltage changes as the external load changes to keep a constant current, and then I'd call it a current source. Ion chambers are also usually considered current sources, since the ion pairs are generated by radiation and source a current.
psparky said:I agree 100%
sirsajid said:What is the difference between neutral and ground??
one more question what is the practical example of current source
metiman said:with AC current the direction of the current is constantly changing 60 times every second. So every 1/30th of a second the white wire is the (positive) 'hot' one.
You ever notice that in almost thread there is someone who has no idea what they are talking about, someone who has some idea, someone who has a pretty good idea what they are talking about, someone who really knows what they are talking about...and then lastly, someone who knows EXACTLY what they are talking about.HORNETD said:This seams a little off topic for a physics forum but a few words of caution are in order so that the answers already given here do not cause someone an injury or worse. I have wired structures from Argentina to Alaska and from Malaysia to Uganda so I am aware that the explanations I am offering here are only applicable to North American practice and some of the other places were a Multi Grounded Neutral system is used for utility power distribution.
Many panel boards are not service equipment / customer service units. That is important because Service equipment is the only place were the "Grounded Current Carrying Conductor;" that most of us call the "Neutral;" is properly earthed or connected to ground. That is done by a conductor that is, in North American Practice, called the main bonding jumper. In panel boards that are not service equipment the Neutral is kept aloof from the "Equipment Grounding Conductor" or ground wire at all times.
The actual grounding / Earthing of the Service Equipment Enclosure is accomplished by connecting it to conductive materials that are buried in the Earth or are effectively functioning as if they are the earth, albeit on a much smaller scale. The Conductive materials that are buried in the Earth are called grounding electrodes. All of the grounding electrodes are deliberately bonded together to form the Grounding Electrode System. The conductor that connects the Service Equipment Enclosure to the Grounding Electrode System is called, strangely enough, the Grounding Electrode Conductor. I guess by that point in the code writing process the code officials were too tired to invent yet another obscure term but I digress. The purpose of Grounding or Earthing the Neutral is to "limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to Earth during normal operation."
The reason for all the specificity is to bring this to an important point. In any system that has Grounded Current Carrying Conductors the voltage drop caused by the normal flow of current in the grounded conductor will raise it's potential above that of the Earth / ground. Further if that "Neutral" becomes damaged or overloaded that voltage above ground can be at a level that is sufficient to cause injurious or destructive current to flow.
For all of these reasons Neutral conductors are not safe to come into contact with until all circuits of which they are a part have been deenergized, locked out and tagged out.
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Tom
jim hardy said:neutral is a wire that returns current from a load
metiman said:Does the hot wire not also 'return' current from load? I don't like the use of 'return' in this context as it seems to imply a direction, but there is no direction in AC.
psparky said:Don't forget that the nuetral comes from a centertapped transformer.
The USA house panel has two legs...one vector at 120 volts...and one vector at -120 volts.
Voltage is the DIFFERENCE between two points. In this case 120 - (-120) = 240 volts. And yes they are rotating vectors, but will always be 180 degrees apart and will always deliver 240 volts when line to line.
cmb said:Sounds like you are describing a 2 phase system. Does USA really have 2 phase domestic supply at the distribution panel? How/where does it convert from 3 phase?
cmb said:Sounds like you are describing a 2 phase system. Does USA really have 2 phase domestic supply at the distribution panel? How/where does it convert from 3 phase?
It's sort of right by saying two phase because you have two different vectors sitting at 180 degrees apart.Averagesupernova said:He is NOT describing 2 phase. It is split-phase, which is still technically single phase.
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Edit: Hmmmm, posted at exactly the same time as psparky.
psparky said:Absolutely. USA does only have line to line single phase in residential panels. I'm not sure I would use the term "two phase"...as this can lead to confusion...but I know what you mean. The transformers located every so often down streets grab to hots (line to line single phase) from the three phase lines above and convert to 240 volt. The transformer also has a center tap or neutral...also called common which is where most of the homes are powered by 120 volt. These 120 volt loads are line to neutral. I think each transformer is only like 15KVA...so that feeds roughly 6 houses or so.
cmb said:Sounds like you are describing a 2 phase system. Does USA really have 2 phase domestic supply at the distribution panel? How/where does it convert from 3 phase?
HORNETD said:No it is definitely single phase. To call it two phase you would be alleging that a multi phase system can be created just by tapping a single transformer secondary winding that is magnetically coupled to a single phase primary winding. If that were in fact true than you could create any number of phases you desired by multi tapping a single transformer winding.
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Tom
cmb said:I don't see what you are saying.
A 'neutral' is a line with [nominally] constant charge on it (hopefully 'net neutral charge', if earthed).
A 'hot' AC line is one with periodic time-varying charge on it.
Two phases are two lines with periodic time-varying charge on them, but of different phase angles.
A two phase system is one with two lines with periodic time-varying charge on them at 180 degree apart. You get this from one phase feeding into a transformer with a grounded centre-tap secondary. The two outputs will be at 180 deg out of phase = two phase.
No, you cannot tap any old number of phases off a simple transformer. If you feed one phase in, you get one phase out of one winding, or two phases out of two windings which might be 180 translated.