How does current flow in a circuit?

[Smart $]

...

OK. Do you have an extra convention adopted that permits you to say the oppossite that my convention adopted do???

I'm not quite certain what you mean... it is basically adoption of said convention or lack thereof. At best, perhaps the concept of "empirical evidence" in the strictest scientific sense...

http://wiki.answers.com/Q/What_is_empirical_evidence
http://en.wikipedia.org/wiki/Empirical
http://en.wikipedia.org/wiki/Empirical_research

PS: The source of current is the material which provides the conductive path of the circuit. The source you refer to provides the voltage and a portion of the conductive material.

 

[Smart $]

PS: Regarding...

While I do not have a copy of Kirchhoff's original work (it would have to be translated for me), I have given you Maxwell's statement of KCL.

...I believe the most accurate translation is:

The algebraic sum of current into any junction is zero.

 

[mivey]

Without the stipulation those interpretting the the other two ways may or will be confused...

Not something I can imagine any competent person would do. I did ignore the possibility of unqualified persons using tools that they are unfamiliar with. I think they assume the responsibility for venturing into areas they should avoid until better schooled.

Not really. But I'm sensing your mind's eye is a bit more open ...

Who knows? Anything is possible. :grin:

First, when we use static phasor analysis for the currents, our magnitudes are always positive due to using the rms value (sure you can negate it and use a 180? phase angle shift if you want... but that too is unnecessary ). Then we associate a cyclic angle with our rms value to specify a point in cycle timing that represents the positive peak of the waveform (again we can use a negative angle if we want, but this too is unnecessary as all angles could be stated as positive less than 360? too, due to the cyclic nature of the beasty ). The two values interassociated describe the waveform. Using vector addition the summing of all currents associated with a node yields a result of zero. No ingoing outgoing methodology to adopt or stipulated

You can make no conclusions with that analysis without adopting a current sense.

Please revisit diagram of post #59. All ammeters have the arrow pointing away from the node they are associated with. This is the prescribed method for taking measurements. As for the needle deflection in the diagram, that is just the way the circuit program draws an ammeter.

Ahh. The old "the devil made me do it excuse". :grin:

In conclusion (I hope ), there is no one best method. I made a modest and simple comment that has blown up into a technobabble nightmare

This site is a great tool for polishing written skills. I have found many times that what I type is not what people read.

 

[mivey]

Really?? You just have make to adopt a condition, and you didnt ask me If I was agree with that. Despite this fact, I dont know why but I got strange feeling about that...

Then quit catering to your feelings and use your reasoning abilities.

Considered. some current goes with P and some other goes with Q, agree. Oh ok, reactive current, I had the believe they were the same thing ("reactive" current and "active" current), I guess I should send some emails for lots of people in the field that didnt know about this. If we keep creating things out of nowhere we will get to a new engineer as well... just saying...

Is that so different from you associating current consumption with power consumption? Have you never used the superposition theorem? I can isolate as many sources as I please. Do you not know that some power plants supply vars to the system and let the others supply watts? The vars to a motor may be coming from a capacitor bank instead of the source supplying the watts.

same as above. why stand and defend on larrys point if you know that deep down, you know theres something strange and messy about the whole "reactive current" idea?

But I have the ability to expand my thoughts beyond the norm where a lot of people stay. We have many on the forum here who are creative thinkers.

quit labelling things without a criteria. "extra current" mislead to many things, and none of them was the one I figured you tried to say the first time. How I could possibly known what you were triying to say??

I have no idea. I am trying to make it as plain as I can.

 

[mivey]

...I believe the most accurate translation is:

If you have found an original or translated copy of his 1854 paper, I would love to obtain a copy. I have looked online but have been unable to find an electronic copy.

 

[Mayimbe]

PS: The source of current is the material which provides the conductive path of the circuit. The source you refer to provides the voltage and a portion of the conductive material.

Good to know that. So the current flows from the source to the load...

we should begin to get to a consensus here.

 

[Mayimbe]

Then quit catering to your feelings and use your reasoning abilities.

fair enough.

1)Is that so different from you associating current consumption with power consumption?
2)Have you never used the superposition theorem? I can isolate as many sources as I please.
3)Do you not know that some power plants supply vars to the system and let the others supply watts? The vars to a motor may be coming from a capacitor bank instead of the source supplying the watts.

1)It isnt different. 2)I have used very often yes. 3)Yes I knew that.

But I have the ability to expand my thoughts beyond the norm where a lot of people stay. We have many on the forum here who are creative thinkers.

Great ability you have.

 

[mivey]

...I have found many times that what I type is not what people read.

To paraphrase a famous line:
"I know that you believe you understand what you think I wrote, but I?m not sure you realize that what you read is not what I meant"

I remember an exercise in writing an instruction set in a technical writing class and it is surprising how many different ways something can be read.

John Weakland: "The meaning of any communication is the response that it gets"

 

[LarryFine]

Here's how I (simplistically) see this issue:

Obviously, and backed up by all of our "the current 'wants' to get back to the source" explanations, there must be just as much current flowing from the load to the source as there is from the source to the load. Plain physics.

What flows only from the source to the load is power. We use the electrical system to transfer energy from one place to another. Just like with phyical wastes, like friction andaerodynamic drag, not all of the energy gets used by the load, but it all must be generated and delivered.

Instead of making a 50-mile long axle shaft from the waterwheel to the millstone, we convert the waterwheel's physical energy into electricity with a generator, and the electricity back into physical energy at the millstone with a motor. The result is work done.

The 50-mile distance bewteen the waterwheel and the millstone is covered by wires that carry current, whether it's AC or DC. That current must flow in both directions; alternately in AC, and continuoulsy in DC. But, it flows equally in both directions.

A clamp-on ammeter or a CT proves that by requiring separation of the circuit conductors to function. If we enclose all conductors, the net result is zero, unless some of that current bypasses the current sensor, which is how a GFCI detects faults.

The point is that we care about getting power from the source to the load. We generate a voltage, and the resulting current is the vehicle that transfers power from one point to the other. The limit is governed by the physical parameters of the equipment.

Any power that does not get used by the load to do the work, but the system will not fiunction without, is wasted energy. Some of it is simple losses, some of it is magnetizing current, some of it is reactive energy. But, it all has to be supplied and carried by the system.


So, my conclusion is that current flows in both directions, and equally so. Reactive power also flows both ways. If it didn't, it would be usable as real power. The real power only flows from the source to the load, and is used to produce the final desired output.

 

[Smart $]

Here's how I (simplistically) see this issue:

...

I think the more anal scientific of readers would say real power is transferred.

 

[Smart $]

Not something I can imagine any competent person would do. I did ignore the possibility of unqualified persons using tools that they are unfamiliar with. I think they assume the responsibility for venturing into areas they should avoid until better schooled.

Okie dokie there, master snooty. If someone didn't impart their knowledge to you, you too would be among the incompetent... and you likely were incompetent in this respect at some point in the past.

You can make no conclusions with that analysis without adopting a current sense.

I'm certain, given n branches and the values of n-1 variables, I can calculate the unknown one (a conclusion) without "adopting a current sense"... so please explain.

 

[mivey]

Okie dokie there, master snooty. If someone didn't impart their knowledge to you, you too would be among the incompetent... and you likely were incompetent in this respect at some point in the past.

I know you can't be suggesting that a novice should jump full force into unfamiliar territory so your comment is petty at best. A person does not have to possess all knowledge to be a competent person. A competent person knows their limitations and acts accordingly. An incompetent person would try to work in an area where they lack the necessary skills to perform the task required.

If it would make you feel better, then substitute proficient, professional, smart, wise, or other such word that brings you comfort.

I'm certain, given n branches and the values of n-1 variables, I can calculate the unknown one (a conclusion) without "adopting a current sense"... so please explain.

You have to make some assumption about the current sense for the n-1 branches or the result for the nth branch is meaningless.

 

[LarryFine]

I think the more anal scientific of readers would say real power is transferred.

As Steve Martin used to say, "Well, excuuuuuuuuuuuse meeeeeeeeeeeeeeeee!"


How did you like my post otherwise?

"Other than that, Mrs. Lincoln, how was the play?"

 

[mivey]

As Steve Martin used to say, "Well, excuuuuuuuuuuuse meeeeeeeeeeeeeeeee!"


How did you like my post otherwise?

"Other than that, Mrs. Lincoln, how was the play?"

I think he summed up his take rather succinctly:

I think the more anal scientific of readers would say...

:grin:
As for me, I thought it was clearly stated and made sense. I hope it translates well for Mayimbe as there seems to be something being lost in the trip across the big pond.

 

[Smart $]

I know you can't be suggesting that a novice should jump full force into unfamiliar territory so your comment is petty at best. A person does not have to possess all knowledge to be a competent person. A competent person knows their limitations and acts accordingly. An incompetent person would try to work in an area where they lack the necessary skills to perform the task required.

If it would make you feel better, then substitute proficient, professional, smart, wise, or other such word that brings you comfort.

Come, come now. The concept of the positve-negative convention is so rudimentary that one doesn't even have to progress to algebra level math to understand its premise. Many even adopt it blindly. Your disposition on the matter is nothing short of condescending.

You have to make some assumption about the current sense for the n-1 branches or the result for the nth branch is meaningless.

Your going to have to define exactly what you mean by "current sense"...

...because having both rms magnitude and phase angle for all but the nth variable leaves nothing to be assumed to solve for the nth variable. In the end, when neutral current is the nth variable, we usually only want to know its rms magnitude and could care less about its phase angle.

 

[Smart $]

...

How did you like my post otherwise?

...

Otherwise excellent, especially considering its brevity and the subject matter.

 

[Pierre C Belarge]

With all the bantering, what I have gotten out of this so far is:
"the ankle bone is connected to the shin bone, the shin bone is connected to the knee bone, the....."


This is a great thread for people who write about communications. I am sure the communications experts would have a field day.

 

[Mayimbe]

Here's how I (simplistically) see this issue:

...

So, my conclusion is that current flows in both directions, and equally so. Reactive power also flows both ways. If it didn't, it would be usable as real power. The real power only flows from the source to the load, and is used to produce the final desired output.

Exactly. Very accurate. This is a good overall view of a electric power system.

As for me, I thought it was clearly stated and made sense. I hope it translates well for Mayimbe as there seems to be something being lost in the trip across the big pond.

Its good for me mivey...

 

[Mayimbe]

I'm certain, given n branches and the values of n-1 variables, I can calculate the unknown one (a conclusion) without "adopting a current sense"... so please explain.

Im just curious... This n-1 variables, are voltage or currents? or what?

You have to make some assumption about the current sense for the n-1 branches or the result for the nth branch is meaningless.

not always, if you have done this calc many times, at the end you will not have to make the assumption of the currents.

[Ybus]*[Vbus]=[Ibus]

Your going to have to define exactly what you mean by "current sense"...

...because having both rms magnitude and phase angle for all but the nth variable leaves nothing to be assumed to solve for the nth variable. In the end, when neutral current is the nth variable, we usually only want to know its rms magnitude and could care less about its phase angle.

rms magnitude and phase angle of voltage?
I believe,
current sense = from where to where does the current flows. assumption. since in reality current flows back and foward.

 

[mivey]

Come, come now. The concept of the positve-negative convention is so rudimentary that one doesn't even have to progress to algebra level math to understand its premise. Many even adopt it blindly. Your disposition on the matter is nothing short of condescending.

Stone-thrower.:grin: It was you who suggested that someone might get confused by the other forms of KCL. My response was that a competent person would not be trying to use a tool without proper instruction. It was you who wanted to start labeling people as incompetent because they did not possess all knowledge. I think labeling someone as incompetent requires a higher burden of proof.

There is nothing wrong with not knowing something. There is something wrong with refusing to admit it, and there is something wrong with using a tool without being versed in its operation. That is when I would say someone is acting incompetently.

Your going to have to define exactly what you mean by "current sense"...

One of two opposite directions in which a line, surface, or volume, may be supposed to be described by the motion of a point, line, or surface.

...because having both rms magnitude and phase angle for all but the nth variable leaves nothing to be assumed to solve for the nth variable. In the end, when neutral current is the nth variable, we usually only want to know its rms magnitude and could care less about its phase angle.

You can't obtain the "proper" phase angles without assigning a direction to the n-1 currents measured.

Without stipulating the sense of the other currents, you can't resolve the nth current.