Electricity question

[JohnCU]

Longest thread of geeks fighting...ever. Except for .999... = 1.

 

[TheLonelyPhoenix]

Originally posted by: 91TTZ
Lonely Phoenix, reading through this thread I've seen you make quite a few put-downs, yet you did not go out of the way to try to help the original poster out. It's easy to sit back and pick apart everyone who sticks their neck out while you never take any risks yourself.

At least I tried to help the guy out, and others have as well. Your intentions are ill.

I'm rather disgusted with the people who walk into these threads, pull an answer completely out of their ass, and insult everyone who tries to tell them they're wrong.

 

[Pepsi90919]

Originally posted by: JohnCU

Originally posted by: Pepsi90919

Originally posted by: JohnCU

Originally posted by: Pepsi90919

Originally posted by: JohnCU

Originally posted by: Pepsi90919

it was already done

It was not done. Ground doesn't alternate. prove that it does.

prove that it doesn't.

Look up the node-voltage method of circuit analysis. That's proof.

no thanks

Okay so stop pulling stuff out your ass and believe me when I say it doesn't alternate.

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..........''...\.......... _.·´
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..............\.............\.

 

[Eli]

Originally posted by: Heisenberg

Originally posted by: Eli

Originally posted by: RaynorWolfcastle

Originally posted by: Eli
Instead of everyone calling everybody else stupid, how about we actually try and learn something?

I found this thread very frustrating. I'm very interested in learning about this stuff, but most of the people that actually know aren't bothering to explain it, they're too busy calling eachother morons.

How much math do you know? Most EM theory requires that you have some pretty advanced math knowledge, ie vector calculus and complex variable math so it's not really all that accessible to the armchair scientist. We used Engineering Electromagnetic Fields and Waves by Johnk but the book is pretty dry and mathematical so I don't know if I'd recommend it to a non-engineer or anyone with a pulse for that matter .

First, can you try and explain what electromagnetic theory has to do with potential, and the OP's question?

Is my assessment of the OP's question correct? "Why can't we measure the potential voltage [with a voltmeter] without completing the circuit?"?

There are basically two different issues here. One is why you can't measure a potential with a DMM without completing a circuit, which is completely a limitation of the equipment. The other is why there is no potential difference between the battery and ground which is a theoretical question, hence the need for the E&M.

I see. Interesting.

I had no idea that there was more depth to it than "There is no circuit.", but then again I've just come into the realization of what potential is somewhat recently.

This thread makes me sad. I'm so interested in electronics, but this just shows me how much I have to learn.

 

[91TTZ]

Originally posted by: TheLonelyPhoenix

Originally posted by: 91TTZ
Lonely Phoenix, reading through this thread I've seen you make quite a few put-downs, yet you did not go out of the way to try to help the original poster out. It's easy to sit back and pick apart everyone who sticks their neck out while you never take any risks yourself.

At least I tried to help the guy out, and others have as well. Your intentions are ill.

I'm rather disgusted with the people who walk into these threads, pull an answer completely out of their ass, and insult everyone who tries to tell them they're wrong.

I walked into the thread, tried my best to help the poster out, and then was insulted by you, who did nothing at all to help anyone out.

 

[Eli]

Originally posted by: TheLonelyPhoenix

Originally posted by: 91TTZ
Lonely Phoenix, reading through this thread I've seen you make quite a few put-downs, yet you did not go out of the way to try to help the original poster out. It's easy to sit back and pick apart everyone who sticks their neck out while you never take any risks yourself.

At least I tried to help the guy out, and others have as well. Your intentions are ill.

I'm rather disgusted with the people who walk into these threads, pull an answer completely out of their ass, and insult everyone who tries to tell them they're wrong.

You still don't understand.

Almost everybody that replied with the "no circuit" response simply read the OP and thought that he was new to electronics. You do understand that, right?

Like I said, even an EE professor wouldn't have broken into some long, drawn out technical explination if he thought the person asking the question had no prior or very little electronics knowledge. Don't you agree?

 

[Heisenberg]

Originally posted by: Eli

Originally posted by: Heisenberg

Originally posted by: Eli

Originally posted by: RaynorWolfcastle

Originally posted by: Eli
Instead of everyone calling everybody else stupid, how about we actually try and learn something?

I found this thread very frustrating. I'm very interested in learning about this stuff, but most of the people that actually know aren't bothering to explain it, they're too busy calling eachother morons.

How much math do you know? Most EM theory requires that you have some pretty advanced math knowledge, ie vector calculus and complex variable math so it's not really all that accessible to the armchair scientist. We used Engineering Electromagnetic Fields and Waves by Johnk but the book is pretty dry and mathematical so I don't know if I'd recommend it to a non-engineer or anyone with a pulse for that matter .

First, can you try and explain what electromagnetic theory has to do with potential, and the OP's question?

Is my assessment of the OP's question correct? "Why can't we measure the potential voltage [with a voltmeter] without completing the circuit?"?

There are basically two different issues here. One is why you can't measure a potential with a DMM without completing a circuit, which is completely a limitation of the equipment. The other is why there is no potential difference between the battery and ground which is a theoretical question, hence the need for the E&M.

I see. Interesting.

I had no idea that there was more depth to it than "There is no circuit.", but then again I've just come into the realization of what potential is somewhat recently.

This thread makes me sad. I'm so interested in electronics, but this just shows me how much I have to learn.

Ah, well we all had to start somewhere. Griffiths' Electrodynamics book is pretty good, but you really need a solid calculus background to make sense of it.

 

[eelw]

Originally posted by: Heisenberg
There are basically two different issues here. One is why you can't measure a potential with a DMM without completing a circuit, which is completely a limitation of the equipment. The other is why there is no potential difference between the battery and ground which is a theoretical question, hence the need for the E&M.

Finally!!!!!! Someone who explained why the closed circuit answer doesn't necessarily answer the OPs question.

 

[TheLonelyPhoenix]

Originally posted by: 91TTZ

Originally posted by: TheLonelyPhoenix

Originally posted by: 91TTZ
Lonely Phoenix, reading through this thread I've seen you make quite a few put-downs, yet you did not go out of the way to try to help the original poster out. It's easy to sit back and pick apart everyone who sticks their neck out while you never take any risks yourself.

At least I tried to help the guy out, and others have as well. Your intentions are ill.

I'm rather disgusted with the people who walk into these threads, pull an answer completely out of their ass, and insult everyone who tries to tell them they're wrong.

I walked into the thread, tried my best to help the poster out, and then was insulted by you, who did nothing at all to help anyone out.

Sure I did. I pointed out everyone who was giving completely wrong answers. Heinsenburg has been giving the correct ones since the beginning, and everyone is ignoring him. Why should I bother even trying after that?

 

[91TTZ]

Originally posted by: Heisenberg

There are basically two different issues here. One is why you can't measure a potential with a DMM without completing a circuit, which is completely a limitation of the equipment. The other is why there is no potential difference between the battery and ground which is a theoretical question, hence the need for the E&M.

As someone whose experience with electronics is limited to testing things with DMM's and oscilloscopes, I didn't know all the theoretical details behind it. I'm sure you can understand why someone who has some experience with electronics but not the in-depth theoretical knowledge of it would think of potentials as something that exists between points in a circuit.

 

[RaynorWolfcastle]

Originally posted by: Eli

Originally posted by: RaynorWolfcastle

Originally posted by: Eli
Instead of everyone calling everybody else stupid, how about we actually try and learn something?

I found this thread very frustrating. I'm very interested in learning about this stuff, but most of the people that actually know aren't bothering to explain it, they're too busy calling eachother morons.

How much math do you know? Most EM theory requires that you have some pretty advanced math knowledge, ie vector calculus and complex variable math so it's not really all that accessible to the armchair scientist. We used Engineering Electromagnetic Fields and Waves by Johnk but the book is pretty dry and mathematical so I don't know if I'd recommend it to a non-engineer or anyone with a pulse for that matter .

First, can you try and explain what electromagnetic theory has to do with potential, and the OP's question?

Is my assessment of the OP's question correct? "Why can't we measure the potential voltage without completing the circuit [with a voltmeter]?"?

As Heisenberg posted a while ago, the potential difference between two points is the integral of the E-field over a path between them. You can pick any path you want to integrate over because E-fields are conservative.

In this case, you can choose the wire, but since the E-field is essentially zero in the wire the integral will sum to zero and you will get 0V potential difference.
That's the long explanation, EM theory explanation.

As for needing to complete the circuit to measure something it's usually a case of practicality. That is, it's usually the easiest way although there may be solutions. You could, for example examine the orientation of polar molecules between the two points you're interested, but that's not really practical.

Just to give you an example where it's somewhat more practical: imagine an AC current flowing through a fixed, known resistance. Clearly there will be a time-varyin potential across the potential across the resistance. By Maxwell's equations (EM theory) we know that the AC current will give rise to a magnetic field. We could measure this magnetic field and use the known value of the resistance to calculate the time varying potential across it. In retrospect, that's not really all that practical, but the example stands.


edit: I apologize if this explanation flies over everyone's head, and confuses more than it helps; that's why I didn't post it in the first place.

 

[91TTZ]

Originally posted by: TheLonelyPhoenix
Sure I did. I pointed out everyone who was giving completely wrong answers.

That still doesn't help much. Imagine if you had a teacher who only told you when you were wrong but never did anything to point students in the right direction.

Your intentions are ill. You were not helpful and didn't mean to be.

 

[Heisenberg]

Originally posted by: 91TTZ

Originally posted by: Heisenberg

There are basically two different issues here. One is why you can't measure a potential with a DMM without completing a circuit, which is completely a limitation of the equipment. The other is why there is no potential difference between the battery and ground which is a theoretical question, hence the need for the E&M.

As someone whose experience with electronics is limited to testing things with DMM's and oscilloscopes, I didn't know all the theoretical details behind it. I'm sure you can understand why someone who has some experience with electronics but not the in-depth theoretical knowledge of it would think of potentials as something that exists between points in a circuit.

Yeah, I can see how that would happen. I only posted because I wanted to make the point that potential is independent of a circuit, and then the thread proceeded in it's downward spiral.

 

[Eli]

Originally posted by: Heisenberg

Originally posted by: Eli

Originally posted by: Heisenberg

Originally posted by: Eli

Originally posted by: RaynorWolfcastle

Originally posted by: Eli
Instead of everyone calling everybody else stupid, how about we actually try and learn something?

I found this thread very frustrating. I'm very interested in learning about this stuff, but most of the people that actually know aren't bothering to explain it, they're too busy calling eachother morons.

How much math do you know? Most EM theory requires that you have some pretty advanced math knowledge, ie vector calculus and complex variable math so it's not really all that accessible to the armchair scientist. We used Engineering Electromagnetic Fields and Waves by Johnk but the book is pretty dry and mathematical so I don't know if I'd recommend it to a non-engineer or anyone with a pulse for that matter .

First, can you try and explain what electromagnetic theory has to do with potential, and the OP's question?

Is my assessment of the OP's question correct? "Why can't we measure the potential voltage [with a voltmeter] without completing the circuit?"?

There are basically two different issues here. One is why you can't measure a potential with a DMM without completing a circuit, which is completely a limitation of the equipment. The other is why there is no potential difference between the battery and ground which is a theoretical question, hence the need for the E&M.

I see. Interesting.

I had no idea that there was more depth to it than "There is no circuit.", but then again I've just come into the realization of what potential is somewhat recently.

This thread makes me sad. I'm so interested in electronics, but this just shows me how much I have to learn.

Ah, well we all had to start somewhere. Griffiths' Electrodynamics book is pretty good, but you really need a solid calculus background to make sense of it.

And such is why *.engineering scares me, even though they're the most interesting things to me.

I suck at math. Not because I can't figure things out.. Dunno. It's hard to explain. I get extremely intimidated and frustrated when presented with math in a school setting.

I would need some serious math-catch up classes to even consider going to school for EE. Algebra is as far as I got.

Sigh.

I've still been trying to learn on my own, though. I have various DIY electronic kits, etc, on order... I seem to learn well by experience, so I figure the more I get to work with it and understand how things work, the better.

 

[TheLonelyPhoenix]

Originally posted by: 91TTZ

Originally posted by: TheLonelyPhoenix
Sure I did. I pointed out everyone who was giving completely wrong answers.

That still doesn't help much. Imagine if you had a teacher who only told you when you were wrong but never did anything to point students in the right direction.

Your intentions are ill. You were not helpful and didn't mean to be.

I'll say it one more time. Before continuing, I'd like you to confirm that you do indeed grasp the ability to read the English language.

Heisenburg has been giving the right answers since the beginning. He was ignored by everyone on here who thought they knew anything about electric circuits. I would have tried to be helpful, but quite honeslty, I'm tired and didn't feel like trying to explain things in a post that was going to be skipped over anyway by people who hit the post button first and read later, such as... yourself.

And for future reference, I'd prefer you quoted my entire post, rather than leaving out the parts which make your responses look stupid.

 

[91TTZ]

Originally posted by: RaynorWolfcastle

As Heisenberg posted a while ago, the potential difference between two points is the integral of the E-field over a path between them. You can pick any path you want to integrate over because E-fields are conservative.

In this case, you can choose the wire, but since the E-field is essentially zero in the wire the integral will sum to zero and you will get 0V potential difference.
That's the long explanation, EM theory explanation.

As for needing to complete the circuit to measure something it's usually a case of practicality. That is, it's usually the easiest way although there may be solutions. You could, for example examine the orientation of polar molecules between the two points you're interested, but that's not really practical.

Just to give you an example where it's somewhat more practical: imagine an AC current flowing through a fixed, known resistance. Clearly there will be a time-varyin potential across the potential across the resistance. By Maxwell's equations (EM theory) we know that the AC current will give rise to a magnetic field. We could measure this magnetic field and use the known value of the resistance to calculate the time varying potential across it. In retrospect, that's not really all that practical, but the example stands.


edit: I apologize if this explanation flies over everyone's head, and confuses more than it helps; that's why I didn't post it in the first place.

While your response (and Heisenburg's) is correct, I think something needs to be said about tailoring the response to the level of the person who asked the question. A response could have been 100% correct but if it flew over the head of the person you were answering, it didn't help them out.

 

[element]

This post has turned into somewhat of a bad neighborhood, I'm moving to highly technical

care to join me? slightly different topic though

 

[JohnCU]

Originally posted by: 91TTZ

Originally posted by: RaynorWolfcastle

As Heisenberg posted a while ago, the potential difference between two points is the integral of the E-field over a path between them. You can pick any path you want to integrate over because E-fields are conservative.

In this case, you can choose the wire, but since the E-field is essentially zero in the wire the integral will sum to zero and you will get 0V potential difference.
That's the long explanation, EM theory explanation.

As for needing to complete the circuit to measure something it's usually a case of practicality. That is, it's usually the easiest way although there may be solutions. You could, for example examine the orientation of polar molecules between the two points you're interested, but that's not really practical.

Just to give you an example where it's somewhat more practical: imagine an AC current flowing through a fixed, known resistance. Clearly there will be a time-varyin potential across the potential across the resistance. By Maxwell's equations (EM theory) we know that the AC current will give rise to a magnetic field. We could measure this magnetic field and use the known value of the resistance to calculate the time varying potential across it. In retrospect, that's not really all that practical, but the example stands.


edit: I apologize if this explanation flies over everyone's head, and confuses more than it helps; that's why I didn't post it in the first place.

While your response (and Heisenburg's) is correct, I think something needs to be said about tailoring the response to the level of the person who asked the question. A response could have been 100% correct but if it flew over the head of the person you were answering, it didn't help them out.

Thanks, but they don't have to dumb it down for me. I've had 2 physics courses and 4 calculus classes, I can follow.

 

[RaynorWolfcastle]

Originally posted by: 91TTZ
While your response (and Heisenburg's) is correct, I think something needs to be said about tailoring the response to the level of the person who asked the question. A response could have been 100% correct but if it flew over the head of the person you were answering, it didn't help them out.

You mean something like this?

Originally posted by: RaynorWolfcastle
The short answer is that there is nothing generating a potential difference between the two prongs of your voltmeter.

 

[Eli]

Originally posted by: TheLonelyPhoenix

Originally posted by: 91TTZ

Originally posted by: TheLonelyPhoenix
Sure I did. I pointed out everyone who was giving completely wrong answers.

That still doesn't help much. Imagine if you had a teacher who only told you when you were wrong but never did anything to point students in the right direction.

Your intentions are ill. You were not helpful and didn't mean to be.

I'll say it one more time. Before continuing, I'd like you to confirm that you do indeed grasp the ability to read the English language.

Heisenburg has been giving the right answers since the beginning. He was ignored by everyone on here who thought they knew anything about electric circuits. I would have tried to be helpful, but quite honeslty, I'm tired and didn't feel like trying to explain things in a post that was going to be skipped over anyway by people who hit the post button first and read later, such as... yourself.

And for future reference, I'd prefer you quoted my entire post, rather than leaving out the parts which make your responses look stupid.

hello.....

I've mentioned this several times, and now 91TTZ has too...

Don't you think the percieved knowledge of the OP had something to do with the way this thread has gone?

Heisenburg's original explination was great and all, but obviously the people that were using the "no circuit" explination aren't going to understand it....

This thread is typical ATOT. One knowledgable person is helpful, but nobody pays any attention to it because other knowledgable people are too busy flaming eachother.

It makes it suck for those of us that are actually interested in learning something.

 

[91TTZ]

Originally posted by: TheLonelyPhoenix

I'll say it one more time. Before continuing, I'd like you to confirm that you do indeed grasp the ability to read the English language.

Heisenburg has been giving the right answers since the beginning. He was ignored by everyone on here who thought they knew anything about electric circuits. I would have tried to be helpful, but quite honeslty, I'm tired and didn't feel like trying to explain things in a post that was going to be skipped over anyway by people who hit the post button first and read later, such as... yourself.

And for future reference, I'd prefer you quoted my entire post, rather than leaving out the parts which make your responses look stupid.

And I'll say it one more time- all of your responses are negative and not helpful at all. The only thing they accomplish is putting people down. I doubt your abilities when all you can do is pick people apart and not be able to help anyone.

That is the difference between smart people and dumb people- a smart person can take a complex subject and make unknowledgeable people understand the concept. A dumb person can take a simple concept and make knowledgeable people get confused or frustrated by it. Einstein was able to give schoolchildren a good grasp of what his theory of relativity was about. You couldn't teach a photographer how to use a camera, mostly because telling them "you are so stupid" doesn't help them much.

 

[JohnCU]

Originally posted by: Eli
hello.....

I've mentioned this several times, and now 91TTZ has too...

Don't you think the percieved knowledge of the OP had something to do with the way this thread has gone?

Heisenburg's original explination was great and all, but obviously the people that were using the "no circuit" explination aren't going to understand it....

This thread is typical ATOT. One knowledgable person is helpful, but nobody pays any attention to it because other knowledgable people are too busy flaming eachother.

It makes it suck for those of us that are actually interested in learning something.

Yeah, I guess I should have specified that I wasn't an idiot with a Walmart voltmeter plugging stuff into the wall.

 

[cressida]

The DC electric potential of a battery is created chemically within. Current is induced in a wire by electrons traveling from one side to the other. In the situation you described, there is no path for the electrons to travel from one terminal of the battery to the other, and therefore no Electric potential or "voltage" is present. This is called an open circuit.

AC is a little different in that the current is induced by the ever changing voltage of the supply. This allows current to flow through a circuit without the electrons ever returning to the source.

These all can be deduced from one of many textbooxs, online resources, high school physics teachers, and non-morons in general.

Edit:

Also, try a few experiments with your voltmeter. Try to measure the voltage of a wall outlet with the meter set to read DC voltage. If you are lucky, your meter will read randomly. . If you are unlucky your voltmeter will be destroyed. Maybe this question is based upon a non zero digital meter reading. Most digital meters will not settle on exactly zero volts. In fact, your proximity to the meter can induce small voltages in the circuitry.

DC and AC are fundamentally different (duh). The voltage of your battery describes the chemical potential between the plates inside it, which are connected to the terminals, NOT any other point. I could go into great depth on this stuff but you would be better off hitting up Google and doing a search for "basic electricity."

Regards.

 

[Eli]

Originally posted by: 91TTZ

Originally posted by: TheLonelyPhoenix

I'll say it one more time. Before continuing, I'd like you to confirm that you do indeed grasp the ability to read the English language.

Heisenburg has been giving the right answers since the beginning. He was ignored by everyone on here who thought they knew anything about electric circuits. I would have tried to be helpful, but quite honeslty, I'm tired and didn't feel like trying to explain things in a post that was going to be skipped over anyway by people who hit the post button first and read later, such as... yourself.

And for future reference, I'd prefer you quoted my entire post, rather than leaving out the parts which make your responses look stupid.

And I'll say it one more time- all of your responses are negative and not helpful at all. The only thing they accomplish is putting people down. I doubt your abilities when all you can do is pick people apart and not be able to help anyone.

That is the difference between smart people and dumb people- a smart person can take a complex subject and make unknowledgeable people understand the concept. A dumb person can take a simple concept and make knowledgeable people get confused or frustrated by it. Einstein was able to give schoolchildren a good grasp of what his theory of relativity was about. You couldn't teach a photographer how to take a picture, mostly because "you are so stupid" doesn't help them much.

EXACTLY.

This is exactly the way I feel, and it's the reason this thread sucks for the most part.

 

[TheLonelyPhoenix]

Originally posted by: 91TTZ

Originally posted by: TheLonelyPhoenix

I'll say it one more time. Before continuing, I'd like you to confirm that you do indeed grasp the ability to read the English language.

Heisenburg has been giving the right answers since the beginning. He was ignored by everyone on here who thought they knew anything about electric circuits. I would have tried to be helpful, but quite honeslty, I'm tired and didn't feel like trying to explain things in a post that was going to be skipped over anyway by people who hit the post button first and read later, such as... yourself.

And for future reference, I'd prefer you quoted my entire post, rather than leaving out the parts which make your responses look stupid.

And I'll say it one more time- all of your responses are negative and not helpful at all. The only thing they accomplish is putting people down. I doubt your abilities when all you can do is pick people apart and not be able to help anyone.

That is the difference between smart people and dumb people- a smart person can take a complex subject and make unknowledgeable people understand the concept. A dumb person can take a simple concept and make knowledgeable people get confused or frustrated by it. Einstein was able to give schoolchildren a good grasp of what his theory of relativity was about. You couldn't teach a photographer how to take a picture, mostly because "you are so stupid" doesn't help them much.

I did try in at least one post to explain things, but obviously you skipped over that too.

My apologies for getting so worked up over this, its been a long day.