What Constitutes Electrical Energy in an Infinite Electrical Field?

[Rutherford]

Okay, so I've been reading about energy and no source seems to make it clear what energy really is. I understand how energy relates to objects in the real world like with moving objects and heated objects, but other forms of energy are more confusing.

Firstly, what is electrical energy? I know that electrical energy is carried in an electrical field, but what is it made of? I don't see how energy can be carried by something that isn't really real. Is it waves? If so, where do these waves come from, and where do these waves travel? If the electrical field stretches to infinity, then is the energy stored in an infinitely large place?

Also, in nuclear fission, where exactly does the energy come from? I get the whole thing about mass turning into energy, but what part of the atom turns to energy? When a neutron collides with an atom, the products have the same atomic mass as the reactants, so what mass is actually being turned into energy? It's clearly not the protons or neutrons, since those all remain with the fission products, so then is it the electrons being turned into energy?

 

[ice109]

energy is ability to do work

mass does not convert to energy, the energy in fission comes from the binding energy inside the nucleus, I'm pretty sure from the strong nuclear force but i could be talking out of my ass here.

 

[Rutherford]

So then what is the binding energy made of?

 

[ice109]

So then what is the binding energy made of?

energy isn't a thing, it is a descriptive characteristic of a particle.

 

[mgb_phys]

It helps to think of energy as not real - it's just there to get the books to balance. Energy is just a concept to make it easier to describe how 'work' gets transferred.
In binding energy the particles really do weight less when in the nucleas - once the extra energy is radiated away.

 

[Rutherford]

Okay, well, then I don't understand how work gets transferred from binding energy in an atom to heat... What happens there? Obviously, something moves from the atom to whatever is being heated, so what is being moved?

 

[Saladsamurai]

So then what is the binding energy made of?

I am not a Chemist or a Physicist, so I am sure that someone can better explain this. But, as I would understand this is that the energy that binds an atom together is not made of anything; it is more like when a weight is held high above the ground, the kinetic, or moving, energy that could be created is a result of the weight's gravitational potential energy. An atom's energy, I believe, arises from the potential energy created by the binding of its subatomic particles.

I know this is a very shoddy explanation, but I am sure someone will correct and enlighten me.

~Casey

 

[Dr. Proof]

In mechanics, kinetic energy is the term given to the mathematical formula Fd=(1/2)mv^2. In everyday use, and even when people try to talk about technical things, the word "energy" gets tossed around extremely loosly. Focus on understanding the mathematical formulas by knowing how to derive them. Physics is not about obtaining some deep ultimate understanding. If you understand where the formulas come from, and if you know how to solve physics problems, then you understand physics.

 

[ice109]

In mechanics, kinetic energy is the term given to the mathematical formula Fd=(1/2)mv^2. In everyday use, and even when people try to talk about technical things, the word "energy" gets tossed around extremely loosly. Focus on understanding the mathematical formulas by knowing how to derive them. Physics is not about obtaining some deep ultimate understanding. If you understand where the formulas come from, and if you know how to solve physics problems, then you understand physics.

what are you talking about? physics is exactly about getting a deep understanding of the way the world works. you come to understand the mathematical formulas by understanding the physical process. if you only know how to solve physics problems you don't know anything.

 

[Rutherford]

Yes... Personally, I don't really care about solving physics problems out of some book. That seems to be what modern day physics has become. I'd like to understand what the physicists have come up with. From what I'm gathering, there is a lack of understanding as to how physics (namely energy) actually works, and I'm trying to solve that problem starting with myself.

I'm fine with an answer of "we don't know what energy is." If that's as far as physics has come, then I'm alright with that. However, I am having trouble believing that's the answer.

What I'm concerned with, I guess, is how does energy work? Like how does that electric field perform work? And how does the splitting of an atom create heat? I just want to know where this stuff is coming from.

 

[ice109]

Yes... Personally, I don't really care about solving physics problems out of some book. That seems to be what modern day physics has become. I'd like to understand what the physicists have come up with. From what I'm gathering, there is a lack of understanding as to how physics (namely energy) actually works, and I'm trying to solve that problem starting with myself.

I'm fine with an answer of "we don't know what energy is." If that's as far as physics has come, then I'm alright with that. However, I am having trouble believing that's the answer.

What I'm concerned with, I guess, is how does energy work? Like how does that electric field perform work? And how does the splitting of an atom create heat? I just want to know where this stuff is coming from.

physics has not become "problem solving", physics what it has always been; explaining phenomena, answering the why.

dude i can sympathize with you but you're asking questions about extremely abstruse things and i get the impression you only have a basic understanding. start from the bottom and work your way to the top, use this curiosity to drive you but don't expect to understand something extremely complex before being able to.

 

[Dr. Proof]

what are you talking about? physics is exactly about getting a deep understanding of the way the world works. you come to understand the mathematical formulas by understanding the physical process. if you only know how to solve physics problems you don't know anything.

Physics is an experimental subject. In physics, one can only understand things experimentally. How do you know that objects fall towards the earth? you would have no reason to believe such a thing unless you saw it for yourself. Physics is not about getting a "deep understanding" as you have said; Physics is about getting a fundamental understanding. For example, objects that fall towards the Earth create a study in and of themselves. You can mathematically describe falling objects and predict the specifics of their motion without having a "deep understanding" of "why" the objects fall towards the earth. Now, Newton's universal law of gravitation helps in mathematically explaining falling objects further; however, Newton's universal law of gravitation does not explain "why" masses exert forces on one another. You see, whenever you ask the question "why", you will never get an ultimate answer, you will always be able to ask "why" one more time. So you see, physicists try to understand things "fundamentally", not "deeply".

 

[ZapperZ]

Yes... Personally, I don't really care about solving physics problems out of some book. That seems to be what modern day physics has become. I'd like to understand what the physicists have come up with. From what I'm gathering, there is a lack of understanding as to how physics (namely energy) actually works, and I'm trying to solve that problem starting with myself.

I'm fine with an answer of "we don't know what energy is." If that's as far as physics has come, then I'm alright with that. However, I am having trouble believing that's the answer.

What I'm concerned with, I guess, is how does energy work? Like how does that electric field perform work? And how does the splitting of an atom create heat? I just want to know where this stuff is coming from.

OK, this may sound highly irrelevant to you, but try to answer this one:

What is an apple?

No, really, try it!

If you do, you will discover for yourself that in answering the question, what you end up doing is listing all the PROPERTIES AND BEHAVIOR of what you define to be an "apple". You will realize that when you ask "what is so-and-so", the ONLY thing that makes any sense is to describe a series of characteristics that are associated with that object in question.

Try it with "electrons", "pumpkins", "my sister", etc...

Now, the same can be said about "energy". The reason why you seem to think it is "ambiguous" is because out of the MANY characteristics of energy, some of them are used in particular situations, while others are used in other situations. However, the other difficulties also is that you appears to have understood only the basic, intro level physics. This is not a criticism. However, because of that, you must also realize that you have BARELY seen the whole picture of how we deal with "energy". For example, you would not have come across the Lagrangian/Hamiltonian mechanics in which there are only TWO forms of energy that really matters in describing the dynamics of any system - kinetic and potential energy of the system. That's it. So one can, in principle, simply answer your question as to what is energy as "kinetic and potential energy", and that's that. In fact, for quantum mechanics, the Hamiltonian of a system consists of just those two terms!

So your "binding energy" for example, gets lumped into the potential term, while any energy of motion such as electricity, would be in the kinetic term. Any EM interaction could either be described via the vector potential, or via operators if we decide to use quantum field theory.

Certainly, there are profound description of what energy is. However, you must also be reasonable on your part to accept that, unless one is willing to put a lot of effort into really studying it, at some point, all that the rest of us can do is simply TELL you that this is so. You are certainly more than welcome to check this yourself by studying up on more advanced topics.

This question gets asked very often, and I think a good search on such a thing will come up with many threads that have already addressed this issue.

Zz.

 

[Rutherford]

I would argue that the question of "What is energy?" is about as basic as it gets right after "What is physics?" Just because it's not explained at the basic level in physics textbooks does not mean that it is not a basic question.

OK, this may sound highly irrelevant to you, but try to answer this one:

What is an apple?

No, really, try it!

Okay, comparing my question to the apple question, I would want to know that an apple is made of proteins, glucose, lipids, whatever it's made of. That's what I'm asking about energy. That's the one specific property that I'm trying to single out. What is it made of?

 

[ice109]

Physics is an experimental subject. In physics, one can only understand things experimentally. How do you know that objects fall towards the earth? you would have no reason to believe such a thing unless you saw it for yourself. Physics is not about getting a "deep understanding" as you have said; Physics is about getting a fundamental understanding. For example, objects that fall towards the Earth create a study in and of themselves. You can mathematically describe falling objects and predict the specifics of their motion without having a "deep understanding" of "why" the objects fall towards the earth. Now, Newton's universal law of gravitation helps in mathematically explaining falling objects further; however, Newton's universal law of gravitation does not explain "why" masses exert forces on one another. You see, whenever you ask the question "why", you will never get an ultimate answer, you will always be able to ask "why" one more time. So you see, physicists try to understand things "fundamentally", not "deeply".

you're arguing semantics. lots of physical theories explain why things happen and not just how. Newton's law of gravitation explains why in the sense that he believed it was axiomatic that masses exterted a gravitational force on each other, and not just how an object travels when it is influenced by gravity. now we're at a point where the constituent particles are the why, if there is something smaller than them and different physics there we will find it and answer the why processes happen question.

 

[ice109]

I would argue that the question of "What is energy?" is about as basic as it gets right after "What is physics?" Just because it's not explained at the basic level in physics textbooks does not mean that it is not a basic question.

Okay, comparing my question to the apple question, I would want to know that an apple is made of proteins, glucose, lipids, whatever it's made of. That's what I'm asking about energy. That's the one specific property that I'm trying to single out. What is it made of?

dude read the tractatus by ludwig wittgenstein, your questions are meaningless and that's not a criticism either but they simply have no meaning. zapper makes a very good analogy.

 

[ZapperZ]

I would argue that the question of "What is energy?" is about as basic as it gets right after "What is physics?" Just because it's not explained at the basic level in physics textbooks does not mean that it is not a basic question.

Okay, comparing my question to the apple question, I would want to know that an apple is made of proteins, glucose, lipids, whatever it's made of. That's what I'm asking about energy. That's the one specific property that I'm trying to single out. What is it made of?

But requiring that all "What is..." must consist of the CONSTITUENTS of the subject doesn't make sense all the time. For example, I could ask "what is the color red?". Do you then describe what "red" is made of? What about "what is time?". This is the same type of question we had before when someone asked for the size of a photon. It is a strange question when a photon was never defined as a regular particle with a definite physical boundary in the first place. That's like asking how heavy is purple.

Do people ask about Force is made of? What about speed or acceleration? Is it made of anything? A "What is... "question need not have the constituents of the object in question as the answer. If you always require that, you'll see many instances where you're asking for absurd answers.

Zz.

 

[ice109]

But requiring that all "What is..." must consist of the CONSTITUENTS of the subject doesn't make sense all the time. For example, I could ask "what is the color red?". Do you then describe what "red" is made of? What about "what is time?". This is the same type of question we had before when someone asked for the size of a photon. It is a strange question when a photon was never defined as a regular particle with a definite physical boundary in the first place. That's like asking how heavy is purple.

Do people ask about Force is made of? What about speed or acceleration? Is it made of anything? A "What is... "question need not have the constituents of the object in question as the answer. If you always require that, you'll see many instances where you're asking for absurd answers.

Zz.

isn't force made of mediating particles?

 

[ZapperZ]

isn't force made of mediating particles?

Not the classical force. Furthermore, a force isn't MADE up of those particles. When you start talking about those force carriers, then you are using the quantum field theory, in which not only the classical field doesn't exist, but the concept of "force" also do not exist. Force, in fact, is replaced by the exchange of these particles. So no, it isn't made up of these particles, but rather the concept has been REPLACED by these particles.

Zz.

 

[ice109]

Not the classical force. Furthermore, a force isn't MADE up of those particles. When you start talking about those force carriers, then you are using the quantum field theory, in which not only the classical field doesn't exist, but the concept of "force" also do not exist. Force, in fact, is replaced by the exchange of these particles. So no, it isn't made up of these particles, but rather the concept has been REPLACED by these particles.

Zz.

yea i knew that statement was nonsensical

 

[Rutherford]

Well, guys... Thanks, I guess... I now know a dozen reasons why you think my question sucks, although I still don't have an answer to it... I've also learned probably another dozen ways to avoid a question by asking other ones...

I probably shouldn't have expected a good answer from the internet, but I thought it would be worth a try at least.

 

[ice109]

Well, guys... Thanks, I guess... I now know a dozen reasons why you think my question sucks, although I still don't have an answer to it... I've also learned probably another dozen ways to avoid a question by asking other ones...

I probably shouldn't have expected a good answer from the internet, but I thought it would be worth a try at least.

that is just down right sullen and insulting. i don't know jack but you atleast got participation from zapper. don't be upset just because you didn't get the answer you wanted.

i'm telling you i sympathize because not only have i been asking question like this for a long time but i made the same exact sullen post on here two weeks ago. what i learned from it is that i need to learn more physics before i can ask questions.

edit

https://www.physicsforums.com/showthread.php?t=172645&highlight=question

there you go my own petulance session

 

[Rutherford]

I don't think that it's your fault or my fault that it's hard to understand. I'm sure we're both perfectly capable of understanding these concepts... It's just that physics is not designed to be understood by laymen like us, and people don't want to try and make it that way. I understand that and I'm not trying to insult anybody. Personally, I find it insulting the way my questions were approached in a way like, "This guy doesn't know all the stuff that I know, so I think I'll let him know that he doesn't deserve to understand."

 

[Saladsamurai]

I don't think that it's your fault or my fault that it's hard to understand. I'm sure we're both perfectly capable of understanding these concepts... It's just that physics is not designed to be understood by laymen like us, and people don't want to try and make it that way. I understand that and I'm not trying to insult anybody. Personally, I find it insulting the way my questions were approached in a way like, "This guy doesn't know all the stuff that I know, so I think I'll let him know that he doesn't deserve to understand."

It has nothing to do with this. Your question was answered many times. I have read the answer many times. Reread through this thread and you will find the answer you requested; whether or not you understand the answer is on you, not us and not Physics itself.

~Casey

 

[ice109]

I don't think that it's your fault or my fault that it's hard to understand. I'm sure we're both perfectly capable of understanding these concepts... It's just that physics is not designed to be understood by laymen like us, and people don't want to try and make it that way. I understand that and I'm not trying to insult anybody. Personally, I find it insulting the way my questions were approached in a way like, "This guy doesn't know all the stuff that I know, so I think I'll let him know that he doesn't deserve to understand."

and I am saying that it cannot be explained in layman's terms.

 

[ZapperZ]

I don't think that it's your fault or my fault that it's hard to understand. I'm sure we're both perfectly capable of understanding these concepts... It's just that physics is not designed to be understood by laymen like us, and people don't want to try and make it that way. I understand that and I'm not trying to insult anybody. Personally, I find it insulting the way my questions were approached in a way like, "This guy doesn't know all the stuff that I know, so I think I'll let him know that he doesn't deserve to understand."

Considering that I have responded with detailed and long answers, and that I have put a lot of effort in trying to put it in ways that can be easily understandable, what you said IS insulting, whether you meant it or not.

You can count on not getting any more assistance from me. This has been a waste of my time.

Zz.

 

[phoenix5002]

Energy would be described as an intrinsic property. Just like mass. Can you describe what mass is without using it in the definition? This goes for energy as well. However, you asked how does energy get transfered, and the answer is through virtual photons. Imagine 2 electrons moving toward each other. When they get close they will transfer their momentum to each other via virtual photons without touching each other, and appear to bounce off one another.

You asked what electrical energy is. Electrical energy through a wire is simply the movement of electrons. The current is positive and is sort of imaginary, the thing that actually moves is the electrons, which travel in the opposite direction of the current, with a negative charge.
One more thing that I find worth mentioning is that the electrons don't travel very fast at all, they actually go very slow. The reason signals are sent instantly is because ALL the electrons along the wire move simultaneously, so if all the the electrons in my internet cable shift 1 atom over then the receiving computer will instantly receive the signal.

 

[Ki Man]

"This guy doesn't know all the stuff that I know, so I think I'll let him know that he doesn't deserve to understand."

The thing is, we don't know either.

Most physicists are content with just saying it is the ability to do work and leaving it at that, and that is a correct statement. Its the 'what is providing them with that ability' that gets us. There isn't much explanation for it. When you get down to the most basic basic particles, the particles are energy, and the energy is communicated in particles. "What is energy" becomes "What is matter" and vice versa.

 

[Ariste]

The thing is, we don't know either.

Most physicists are content with just saying it is the ability to do work and leaving it at that, and that is a correct statement. Its the 'what is providing them with that ability' that gets us. There isn't much explanation for it. When you get down to the most basic basic particles, the particles are energy, and the energy is communicated in particles. "What is energy" becomes "What is matter" and vice versa.

And then you ask, what are they both?

What is energy is really an interesting question, but, like others have pointed out, it's nearly unanswerable. It is described as the ability to do work, but that's not what you're looking for. You're searching for a physical description of what energy is. What it looks like, what it feels like - in the same way, as you said, that an apple is made of proteins and lipids.

The thing is, we're talking about elementary particles here. Perhaps energy is the most elementary of all particles. Indeed, E does equal mc^2. Mass is energy. At some point, you can't ask what something is made of. It just is. You have atoms, which are made of nucleons and electrons, which are made of quarks, which are, if you believe string theory, made of vibrating strands of energy. Where do you go from there? Energy is just energy. It is the base level. Everything else is made up of it. I don't think there's any deeper you can go.

In one way of looking at it, what you are asking is a question I have recently been asking myself: what does it mean to exist? Mass and force and energy exist, but what does that mean? If energy is the base level - if it has no constituents - all we can do to describe it besides list its characteristics is to say that it exists. What does that mean? I have no idea.

 

[john caley]

The truth is physicists really have no idea about much of what is classed as physics.

Their world has become extremely fanciful, where experiment is no longer required to form theory.

Gravity is not understood, nor is mass, force, energy, acceleration etc

Oh yes, mathematics is understood, unfortunately with mathematics you can prove almost anything.

NASA uses Newtonian mechanics to guide its spacecraft , and physics on Earth have progressed no further than merchants of old.

Oh yes we noticed fissionable material heated up when pure ----> A bomb etc, and yes we have noticed plenty, but is it all real ?

That really is the question.

 

[russ_watters]

Well, guys... Thanks, I guess... I now know a dozen reasons why you think my question sucks, although I still don't have an answer to it... I've also learned probably another dozen ways to avoid a question by asking other ones...

I probably shouldn't have expected a good answer from the internet, but I thought it would be worth a try at least.

You're still not getting it - it the problem isn't that we were unable to provide you with a good answer to your question, it is that you were unable to ask a meaningful question for us to answer.

We most certainly understand the concept of energy here and the answers you got were as good as answers to questions about the nature of energy get.

 

[rewebster]

The truth is physicists really have no idea about much of what is classed as physics.

Their world has become extremely fanciful, where experiment is no longer required to form theory.

Gravity is not understood, nor is mass, force, energy, acceleration etc

Oh yes, mathematics is understood, unfortunately with mathematics you can prove almost anything.

NASA uses Newtonian mechanics to guide its spacecraft , and physics on Earth have progressed no further than merchants of old.

Oh yes we noticed fissionable material heated up when pure ----> A bomb etc, and yes we have noticed plenty, but is it all real ?

That really is the question.

This question will give you something to do in your spare time--like it did Einstein for the last 20 or 30 years of his life.

 

[phoenix5002]

Gravity is not understood, nor is mass, force, energy, acceleration etc

Oh yes, mathematics is understood, unfortunately with mathematics you can prove almost anything.

NASA uses Newtonian mechanics to guide its spacecraft , and physics on Earth have progressed no further than merchants of old.

I must dissagree with saying that acceleration is not understood. I'm pretty sure I have a very firm understanding of acceleration.
Also, I do believe that NASA uses a lot of special/general relativity to guide it's ships and sattelites.

Sorry to argue over small things irrelevant of the topic, but I feel that this discussion is about over so I thought I'd argue a few trifles.

 

[Neutralino]

If energy is an ability, what about quanta, packets of energy? what are quarks and leptons made of?
And the strong nuclear force binds the nucleon together, not the energy. Anyway, I think that energy is the interactions between the fundamental particles through the fundamental forces.

 

[rewebster]

I must disagree with saying that acceleration is not understood. I'm pretty sure I have a very firm understanding of acceleration.

I think it can be calculated, maybe, to the 6th decimal place.

 

[pmb_phy]

Okay, so I've been reading about energy and no source seems to make it clear what energy really is. I understand how energy relates to objects in the real world like with moving objects and heated objects, but other forms of energy are more confusing.

Firstly, what is electrical energy? I know that electrical energy is carried in an electrical field, but what is it made of? I don't see how energy can be carried by something that isn't really real. Is it waves? If so, where do these waves come from, and where do these waves travel? If the electrical field stretches to infinity, then is the energy stored in an infinitely large place?

Also, in nuclear fission, where exactly does the energy come from? I get the whole thing about mass turning into energy, but what part of the atom turns to energy? When a neutron collides with an atom, the products have the same atomic mass as the reactants, so what mass is actually being turned into energy? It's clearly not the protons or neutrons, since those all remain with the fission products, so then is it the electrons being turned into energy?

My website may be of help on this question. See

http://www.geocities.com/physics_world/mech/what_is_energy.htm

Mass is never converted into energy. During fission or fussion what happens is that the total inertial mass (aka relativistic mass) remains constant. Only the form of mass changes. E.g. mass of potential energy changes to mass of kinetic energy. That is what people mean when they say that mass to be converted to energy.

Pete

 

[russ_watters]

Btw, no one answered this part:

When a neutron collides with an atom, the products have the same atomic mass as the reactants...

That isn't a nuclear reaction. A nuclear reaction involves splitting or combining atoms and the mass most certainly is not constant.

Okay, well, then I don't understand how work gets transferred from binding energy in an atom to heat... What happens there? Obviously, something moves from the atom to whatever is being heated, so what is being moved?

Heat energy is radiated electromagnetically: ie, light.


Again, regarding the core problem here:

I don't think that it's your fault or my fault that it's hard to understand. I'm sure we're both perfectly capable of understanding these concepts... It's just that physics is not designed to be understood by laymen like us, and people don't want to try and make it that way. I understand that and I'm not trying to insult anybody. Personally, I find it insulting the way my questions were approached in a way like, "This guy doesn't know all the stuff that I know, so I think I'll let him know that he doesn't deserve to understand."

Physics most certainly can be understood by laymen. The problem is that you are simply not accepting the knowledge people are giving you. Yes, I'm sure you are capable of understanding these concepts - you simply refuse to do so. Unless you decide to be willing to learn, you won't.

 

[rcgldr]

Energy - the capacity to do work.

It would help if an simple example were used. A battery is a good example. Batteries have "a capacity to do work". The electrical energy from a battery can be used to drive a motor, which in turn could lift an object, peforming work on the object. The amount of work done would be the weight of the object times the distance the object was raised. The battery would use up it's energy while lifting the object, until the battery no longer had any energy, and then the object would stop being lifted. If there were no losses in the system, then the amount of work done in lifting the object when it stopped moving would indicate the amount of energy that the battery had at the start.

Using real numbers, say a 12 volt battery is rated at two amp hours. Assume it's an ideal battery that outputs 12 volts independent of load and remains at 12 volts until it's energy runs out and it drops to 0 volts instantly. The battery has 24 watt hours of energy or 24x3600 = 86400 watt seconds = 86400 joules of energy. A joule is the amount of work it takes to applie a force of Newton for a distance of one meter. Gravity applies a force of 9.8 Newtons to a 1kg object, so it takes 9.8 joules of work to raise a 1kg object one meter. So this 86400 joule battery could raise a 1kg object 86400 / 9.8 ~= 8816 meters in a idealized lossless environment.

Reversing the situation, say the battery is rechargable, and the motor is replaced by a generator that charges the battery. Assuming the system is lossless, then allowing the weight to lower 8816 meters by turning the generator would generate 86400 joules of energy, recharging the battery back to it's former state.

So the 1kg object at a height of 8816 meters has 86400 joules of "potential energy", same as the 12 volt 2 amp hour battery, and both can be used to perform 86400 joules of work.

 

[pmb_phy]

Energy - the capacity to do work.

One of the reasons that Richard Feynman states that nobody knows what energy is is because a definition has yet to be found that is near what we believe energy should be defined to be. For instance, here you define "energy" as the capacity to do work. Yet the same thing can be said of both potential and kinetic energy (even mass-energy) but it is the sum of all these quantities that we call "energy" in classical mechanics.

Pete

 

[russ_watters]

I'm not sure I see your point, pete - why should different forms of energy be treated differently?

If you need to lift a 1kg object 1m, it doesn't matter from what form the energy to do that comes - whether electrical, mechanical potential or kinetic, etc., it is still just 10n-m of work.

 

[pmb_phy]

I'm not sure I see your point, pete - why should different forms of energy be treated differently?

If you need to lift a 1kg object 1m, it doesn't matter from what form the energy to do that comes - whether electrical, mechanical potential or kinetic, etc., it is still just 10n-m of work.

My point is that different forms of energy is just that, different forms of energy. It is not what energy itself is. That is an astract concept

The sum of all types of energy is the total energy (just as E = K + U = total mechanical energy) and that's what we give the name "energy". We don't call that kinetic energy nor do we call it potential energy. Its just energy. Calling it the capacity to do work one might think you were trying to define potential energy.

Richard Feynman has for a long time had a great influence on me. The topic "What is energy?" comes upin his Volume I of the Feynman Lectures.

From The Feynman Lectures on Physics - Vol. I, by Feynmann, Leighton, and Sands, page 4-2. This is also quoted on the web page I posted the URL top in my first post in this thread (which it appears you didn't read?)

It is important to realize that in physics today, we have no knowledge of what energy is. We do have a picture that mass comes in little blobs of a definite amount. It is not that way. However, there are formulas for calculating some numerical quantity, and when we add them together it all gives "28"-always the same number. It is an abstract thing in that it does not tell us the mechanism or the reasons for the various formulas.

When I think of a definition for energy this is what always crosses my mind.

When it comes to "The capacity to do work" - This is the definition of potential energy as given in Classical Dynamics of Particles & Systems - 3rd Ed., Marion and Thornton, Harcourt-Brace-Jovanovich, (1988)

Pete

 

[leright]

My point is that different forms of energy is just that, different forms of energy. It is not what energy itself is. That is an astract concept

The sum of all types of energy is the total energy (just as E = K + U = total mechanical energy) and that's what we give the name "energy". We don't call that kinetic energy nor do we call it potential energy. Its just energy. Calling it the capacity to do work one might think you were trying to define potential energy.

Richard Feynman has for a long time had a great influence on me. The topic "What is energy?" comes upin his Volume I of the Feynman Lectures.

From The Feynman Lectures on Physics - Vol. I, by Feynmann, Leighton, and Sands, page 4-2. This is also quoted on the web page I posted the URL top in my first post in this thread (which it appears you didn't read?)

When I think of a definition for energy this is what always crosses my mind.

When it comes to "The capacity to do work" - This is the definition of potential energy as given in Classical Dynamics of Particles & Systems - 3rd Ed., Marion and Thornton, Harcourt-Brace-Jovanovich, (1988)

Pete

Even kinetic energy has the capacity to do work, pete. If a ball with 5 joules of KE collides elastically with a second ball at rest, and all of the first ball's KE is transferred to the second ball, then 5 joules of work has also been done on the second ball.

If we are dealing with inelastic collisions then the 'missing KE' shows up as heat, sound, or PE. And really, heat and sound are just forms of KE.

 

[rcgldr]

Although some forms of energy are relative to a frame of reference, such as gravitational potential energy and kinetic energy, the example I used, a battery, has an energy capacity that isn't sensitive to a frame of refernce. Also I'm assumed that the OP wanted a simple explanation.

 

[pmb_phy]

Even kinetic energy has the capacity to do work, pete.

Thanks. I'm well aware of that. In fact I mentioned that in the firste draft of this post but decided that it was already known to the reader. If "The capacity to do work" is (total) "energy" and kinetic energy is "The capacity to do work" and potential energy is "The capacity to do work" then potential energy = kinetic energy = (total) energy. kinetic energy and kinetic energies are forms of energy. Take, for instance, what would happen if we were to attempt to difine life. How would you do that? Would you say that any bilogical entity that walks on two legs is alive, it really doesn't get you closer to finding out what life is. You can give us numerable examples of life and yet we'd have no definition of it. This same idea also applies to energy

Pete

 

[TuviaDaCat]

if its mechanics were talking about:
isnt energy a mathematical term?
we have just derived by the laws of Newton a quantity which is constant: E=KE+PE, and it helps finding more easily more interesting characteristics of a body, such as speed.

 

[rewebster]

One of the reasons that Richard Feynman states that nobody knows what energy is is because a definition has yet to be found that is near what we believe energy should be defined to be. For instance, here you define "energy" as the capacity to do work. Yet the same thing can be said of both potential and kinetic energy (even mass-energy) but it is the sum of all these quantities that we call "energy" in classical mechanics.

Pete

This is sort of the way I look at it, but I'll go a step in a different direction:

If you're an APPLIED physicist (most researchers, some teachers, most engineers, etc.), just about all or everything you want to know about energy is there/known to be utilized--a formula for every need.

However, if you are more interested in the fundamental, theoretical aspects of energy, it is full of unknowns. This is why there isn't a viable TOE, GUT, UFT, or whatever line (theory base) you want to adhere, to call it a theory of it all to answer the question. That's why there's so many competing theories right now, and why they need different 'addendums (addendi ?)' to work on different 'things' and 'levels'/'sizes' to work 'more' accurately with the different theories.

It more or less depends on what you want to do with your 'energy'.

 

[pmb_phy]

if its mechanics were talking about:
isnt energy a mathematical term?

Yes, as is most, if not all, of the energy forms that I know of.

Pete

 

[leright]

Thanks. I'm well aware of that. In fact I mentioned that in the firste draft of this post but decided that it was already known to the reader. If "The capacity to do work" is (total) "energy" and kinetic energy is "The capacity to do work" and potential energy is "The capacity to do work" then potential energy = kinetic energy = (total) energy. kinetic energy and kinetic energies are forms of energy. Take, for instance, what would happen if we were to attempt to difine life. How would you do that? Would you say that any bilogical entity that walks on two legs is alive, it really doesn't get you closer to finding out what life is. You can give us numerable examples of life and yet we'd have no definition of it. This same idea also applies to energy

Pete

no, 'energy' is the capacity to do work, and it can have kinetic and potential energy components. PART of the capacity to do work is due to kinetic energy and PART is due to potential energy. The fact of the matter is, all energy, regardless of its form, has the capacity to do work. 5 J of energy, no matter its form, can do 5 J of work. Thus, it is possible to simply say 'energy is the capacity to do work'.

At least this is how I understood it. If an object has 5 J of PE and 5 J of KE then it has 10 J of total energy and therefore it can do 10 J of work on another object.

 

[pmb_phy]

no, 'energy' is the capacity to do work, [./quote]Is there a reason you need to repeat this to me? It was this "definition" that I was disagreeing with. As far as that goes its impossible to logiocally say that I'm wrong since we're arguing definition. At best (and more polite) way to approach your response the logical way is to disagree with me.

How would you explain that while this work is being done that the energy itself never changes.

Its okay if you want to define it that way. I choose differently. Why? Because Feynman response to the question "What is energy?" is perfectly reasonable to me and is better phrased than anything I've ever seen.

I posted only a very small summation of that section in the Feynman Lecutress V-II. I recommend that you find a copy and read his entire explanation for his answer. I posted only his answer, not his reasoning for it.

As far as "Energy is the capacity to do work" - why do you think Marion and Thornton defined potential energy as the "capacity to do work"??

I understand what you hold the definition to be and its been stated manyt times in this thread. I'm not nuts you know. I did understand your point. I just happen to strongly disagree with it for very strong reasons. So there is no need to further state "Energy is the capacity to do work."

Pete

 

[Cyrus]

But pete, energy is the capacity to do work!