What type of energy does electrical current have?

[franjo]

I'm interested in what kind of energy has electric current ?. For everything I taught in school should have kinetic energy because electrons are on a certain potential within the electric field when the switch is closed then the electrons move and the electric current is "generated" which then should have the kinetic energy. And so I was thinking all the time until I came across this article http://amasci.com/miscon/ener1.html which actually tells me that everything I know about the electric current is wrong On the other hand, I wonder if so many books from college ,schools, are spoken in the wrong way It's just a little weird that a huge number of scientists and engineers are actually talking nonsense all the time and so I hope that you can help me clarify my dilemma.

thanks in advance.

 

[paulo84]

I'm interested in what kind of energy has electric current ?. For everything I taught in school should have kinetic energy because electrons are on a certain potential within the electric field when the switch is closed then the electrons move and the electric current is "generated" which then should have the kinetic energy. And so I was thinking all the time until I came across this articlehttp://amasci.com/miscon/speed.html which actually tells me that everything I know about the electric current is wrong On the other hand, I wonder if so many books from college ,schools, are spoken in the wrong way It's just a little weird that a huge number of scientists and engineers are actually talking nonsense all the time and so I hope that you can help me clarify my dilemma.

thanks in advance.

Where does the link say it's not kinetic energy? Confused here.

 

[franjo]

Where does the link say it's not kinetic energy? Confused here.

sorry the wrong link this is correct
http://amasci.com/miscon/ener1.html

 

[paulo84]

Oh right. I was also taught it the same way as you. Curious to see more replies.

 

[franjo]

Oh right. I was also taught it the same way as you. Curious to see more replies.

no problem I hope we will get answers

 

[sophiecentaur]

Where does the link say it's not kinetic energy? Confused here.

You want a way into Physics and this is an ideal way to start. You can find for yourself, how much energy would be transferred if it were all in the KE of electrons? The numbers are extremely important in understanding any physical phenomenon.
You could find it useful to google "electron drift velocity" and, using a value in that range, work out how much Kinetic Energy all the conduction electrons in a piece of conducting metal could be carrying. Assume you have 1gram of metal (0.01kg) and work out the total mass of conduction electrons (one for each atom). Use
KE = mv²/2 for the total KE. Then consider that a piece of metal wire could be transporting many kJ of energy per second (kW). How does your result compare with that?

 

[paulo84]

You want a way into Physics and this is an ideal way to start. You can find for yourself, how much energy would be transferred if it were all in the KE of electrons? The numbers are extremely important in understanding any physical phenomenon.
You could find it useful to google "electron drift velocity" and, using a value in that range, work out how much Kinetic Energy all the conduction electrons in a piece of conducting metal could be carrying. Assume you have 1gram of metal (0.01kg) and work out the total mass of conduction electrons (one for each atom). Use
KE = mv²/2 for the total KE. Then consider that a piece of metal wire could be transporting many kJ of energy per second (kW). How does your result compare with that?

I looked up drift velocity as you suggested. Judging from the wikipedia article it sounds like both the kinetic and electrical energy are factors?

 

[sophiecentaur]

I looked up drift velocity as you suggested. Judging from the wikipedia article it sounds like both the kinetic and electrical energy are factors?

So work out an actual value for KE in a typical example. You really need to do a bit of graft here, you know.

 

[paulo84]

So work out an actual value for KE in a typical example. You really need to do a bit of graft here, you know.

Thanks, I spent enough time doing maths in sixth form.

 

[paulo84]

Fine, you win. I'll do it later, I have been awake for many, many, many hours.

 

[jartsa]

I'm interested in what kind of energy has electric current ?. For everything I taught in school should have kinetic energy because electrons are on a certain potential within the electric field when the switch is closed then the electrons move and the electric current is "generated" which then should have the kinetic energy. And so I was thinking all the time until I came across this articlehttp://amasci.com/miscon/speed.html which actually tells me that everything I know about the electric current is wrong On the other hand, I wonder if so many books from college ,schools, are spoken in the wrong way It's just a little weird that a huge number of scientists and engineers are actually talking nonsense all the time and so I hope that you can help me clarify my dilemma.

thanks in advance.

I guess the answer is "magnetic energy".

And the path to a deeper answer involves explaining the "magnetic energy". Probably "magnetic energy" can be explained by special relativity. Because "magnetism" can be explained by special relativity.
So let's say we have many separated electrons, and we accelerate them all to the same velocity. We gave the electrons kinetic energy.

Now we force those moving electrons close to each other, without changing the velocity of the gas. We can not do that without increasing the momentum of the gas. Because energy has momentum in special relativity. Here we gave the gas "magnetic energy".

 

[sophiecentaur]

I guess the answer is "magnetic energy".

Electromagnetic energy.

 

[franjo]

Fine, you win. I'll do it later, I have been awake for many, many, many hours.

Electromagnetic energy.

thanks for the answers but no one answered my question

 

[Dale]

I'm interested in what kind of energy has electric current ?.

The type of energy that an electric current has is electromagnetic energy. It is described by Poynting’s theorem.

electric current is "generated" which then should have the kinetic energy.

In typical circuits the KE of the electrons is utterly negligible. To see how negligible, please follow the approach suggested by @sophiecentaur

It's just a little weird that a huge number of scientists and engineers are actually talking nonsense

In classical EM the flow of energy is given by Poynting’s theorem. However, under the right conditions, you can simplify Maxwell’s equations to the equations of circuit theory. In circuit theory $P=IV$, which can give the false impression that the power is localized to the current.

 

[franjo]

The type of energy that an electric current has is electromagnetic energy. It is described by Poynting’s theorem.

In typical circuits the KE of the electrons is utterly negligible. To see how negligible, please follow the approach suggested by @sophiecentaur

In classical EM the flow of energy is given by Poynting’s theorem. However, under the right conditions, you can simplify Maxwell’s equations to the equations of circuit theory. In circuit theory $P=IV$, which can give the false impression that the power is localized to the current.

ok in this system what is purpose of voltage and current i don't understand

 

[jartsa]

thanks for the answers but no one answered my question

Oh. I understood literally the question "what type of energy does electric current have".

Maybe the real question is "what energy do we have when quite many electrons are packed in a quite small volume". Like when a lightning strikes through a cellphone mast.

 

[Dale]

ok in this system what is purpose of voltage and current i don't understand

I don’t understand your question. Are you asking about why an electrical engineer might choose a particular voltage and current?

 

[franjo]

I don’t understand your question. Are you asking about why an electrical engineer might choose a particular voltage and current?

the whole problem is in misunderstanding may question

i'm interested in what kind of energy has electric current kinetic ,potential,magnetic,mechanical ?. For everything I taught in school should have kinetic energy because electrons are on a certain potential within the electric field when the switch is closed then the electrons move and the electric current is "generated" which then should have the kinetic energy. And so I was thinking all the time until I came across this article http://amasci.com/miscon/ener1.html which actually tells me that everything I know about the electric current is wrong On the other hand, I wonder if so many books from college ,schools, are spoken in the wrong way It's just a little weird that a huge number of scientists and engineers are actually talking nonsense all the time and so I hope that you can help me clarify my dilemma.

thanks in advance.

if you read this http://amasci.com/miscon/ener1.html article you will understand what is my dilemma

 

[sophiecentaur]

i'm interested in what kind of energy has electric current kinetic ,potential,magnetic,mechanical ?

I think you could be wasting your time here, with that approach. You seem to think that Classifying the Energy in some way will help your understanding of the processes of Energy Transfer. The Mechanism of Energy Transfer, whatever the case, is sometimes helped and sometimes not helped by trying to identify an intermediate 'type' of energy. So the energy imparted to a turbine can sometimes be discussed in terms of the kinetic energy of flying drops of water hitting the blades. However, the Kinetic Energy of the water in a conventional water wheel, is a small part of the power transfer - the ideal design, involving very slow water entering the top buckets and then the water leaving the bottom buckets also at slow speed. The Energy in that case is (largely) due to a change in Potential Energy due to the change in height. Which explanation is 'right'? It depends on the particular case. Same with electrical power. If you bombard a target inside a vacuum with high speed electrons or ions then the heating effect can be calculated in terms of the KE of the particles. That KE, of course, is gained as the charges 'fall' through a large Potential Difference (accelerated by the Field). In a metal, they do not speed up. Same correct answer in each calculation. Which one do you want?

so many books from college ,schools, are spoken in the wrong way

Can you actually quote the wording in a book that tells you the energy to a bulb is delivered with KE?

 

[lekh2003]

Fine, you win. I'll do it later, I have been awake for many, many, many hours.

Get some good sleep, the forum runs 24/7. There was actually a guy on the forum a little while back who ended up getting himself banned due to lack of sleep (I don't want to get into it).

 

[Dale]

i'm interested in what kind of energy has electric current kinetic ,potential,magnetic,mechanical ?

The energy is electromagnetic.

For everything I taught in school should have kinetic energy

Did you perform the calculation suggested by @sophiecentaur ? If so, what do you conclude? Does the KE in a typical circuit represent a substantial amount or is it negligible?

I wonder if so many books from college ,schools, are spoken in the wrong way It's just a little weird that a huge number of scientists and engineers are actually talking nonsense all the time

It certainly is possible. Nonsense is often taught, sometimes on purpose (lies to children), sometimes accidentally (mistaken teachers).

However, it is also possible that you misunderstood the sources and that they were not claiming what you thought.

Most likely it is a combination of both. There is no way to know without reviewing the specific source.

 

[russ_watters]

the whole problem is in misunderstanding may question

i'm interested in what kind of energy has electric current kinetic ,potential,magnetic,mechanical ?.

I don't understand why you keep asking the same question, including the correct answer in as an option and then repeating the question when the answer is given to you. It makes no sense.

For everything I taught in school should have kinetic energy because electrons are on a certain potential within the electric field when the switch is closed then the electrons move and the electric current is "generated" which then should have the kinetic energy. And so I was thinking all the time until I came across this article http://amasci.com/miscon/ener1.html which actually tells me that everything I know about the electric current is wrong...

I can't tell if that article has quality information in it because it is presented so badly. It looks like it came from a 20 year old forum discussion! There are plenty of good articles on how it works. For example:
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepow.html

ok in this system what is purpose of voltage and current i don't understand

Well, you multiply them together to get power. Power is energy transferred per unit of time. You asked the purpose, but do you know what those two words means? Is that what you are really asking?

 

[David Lewis]

Circuit theory solves a wide range of useful problems using a simplified, unrealistic model that should not be taken too literally.

 

[Dale]

Circuit theory solves a wide range of useful problems using a simplified, unrealistic model that should not be taken too literally.

I don’t think that there is any reason to not take the model literally. The problem is in using the model to make claims that the model doesn’t make.

In circuit theory there is no location. The position of a capacitor or the geometry of a wire is not part of the model. So while P=IV tells you literally that the power transferred is equal to the current times the voltage it does not tell you anything about where that energy is located. It cannot possibly tell you that because location has been removed from the model!

The problem comes when people look at P=IV and conclude that the power is located inside the current. The model doesn’t say that, because the model cannot say that.

 

[russ_watters]

I don’t think that there is any reason to not take the model literally. The problem is in using the model to make claims that the model doesn’t make.

[Double-like]
So true and such a big problem with teaching/learning; understanding the usefulness and boundaries of a model...or spending more time arguing about it than using it.

In circuit theory there is no location. The position of a capacitor or the geometry of a wire is not part of the model. So while P=IV tells you literally that the power transferred is equal to the current times the voltage it does not tell you anything about where that energy is located. It cannot possibly tell you that because location has been removed from the model!

The problem comes when people look at P=IV and conclude that the power is located inside the current. The model doesn’t say that, because the model cannot say that.

The way I first read that (probably just before the second paragraph) sounded kind of odd, so I'll repeat it backwards:

Energy is always a system property, not an object property. It's a relationship between "things", not an independent property of things. A unit of charge or a cubic meter of water doesn't "have energy" that can be changes or transferred to something else without other relationships and properties being part of the description.

What you can somewhat localize about it in DC circuits is by drawing a tighter system boundary that doesn't contain the whole circuit. Then you can you can figure out and say somewhat local things like "this resistor absorbs/dissipates that much power".

 

[Dale]

So true and such a big problem with teaching/learning; understanding the usefulness and boundaries of a model..

I agree. I think that curriculum developers would help a lot if every time they introduced a model they included a couple of homework questions where a student simply needs to identify if a model applies for a given scenario and if not which model assumption is violated.

What you can somewhat localize about it in DC circuits is by drawing a tighter system boundary that doesn't contain the whole circuit. Then you can you can figure out and say somewhat local things like "this resistor absorbs/dissipates that much power".

Yes, the resistor is a feature of the model and the model correctly identifies how much power it dissipates. What the model does not do is specify that the power enters the resistor on the end where the current comes in as opposed to the sides of the resistor. The end of the resistor and the sides of the resistor are not features in the model. The model makes no claim of where the power flows into the resistor, just how much.

 

[Delta2]

The current has kinetic energy of the moving charges that constitute it. BUT the most important thing is that it also has potential energy cause the moving charges are inside an electromagnetic field. It is this potential energy from where the work done on the moving charges by the field is coming from. For example inside a resistor the electrons of the current have potential energy cause they are inside an electric field, which accelerates them and gives them kinetic energy which afterwards is converted to heat as the electrons collide with the ion atoms of the resistor.