Should “energy” be redefined?

[onepower]

Energy is easy to understand if put in the right context.

Energy = Work(Force x Distance) x Time

For example, The electrical Force in Volts x the Distance the electrons flow measured in amps gives us the work performed in Watts which we call power. However the Energy is (Work x Time), which is the power flowing in Watts x the Time it was flowing giving us the Energy in Watt-seconds or kW-hr's.

The Joule is simply a universal unit of Energy equal to one Watt/second. That is one Watt of work performed for a time period of one second.

The concept of Energy applies to everything on every level, a Force is applied to something causing the something to move a Distance and Force x Distance equals Work. How much work is done over a given period of time is Energy.

Regards

[bistander]

Hi onepower,
I have a few comments.

Energy is easy to understand if put in the right context.

Energy = Work(Force x Distance) x Time
...

I disagree. The standard definition is that energy is equal to work, not work times time. You often see the equation E = Ws which is saying that energy (E) = power (W) * seconds (s).

Work is not represented by the symbol W. Work is energy and carries the units of joules. A joule is equal to a watt second. 1J = 1W * 1s = 1Ws.

Work is equal to force times distance. Work in joules = force in newtons times distance in meters. Since work is energy, it is represented by the symbol E. So E (joules) = F (newtons) * d (meters). 1J = 1N * 1m. Joule = Newton meter.

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For example, The electrical Force in Volts x the Distance the electrons flow measured in amps gives us the work performed in Watts which we call power. However the Energy is (Work x Time), which is the power flowing in Watts x the Time it was flowing giving us the Energy in Watt-seconds or kW-hr's.
...

Volts times amps is not work, as you state in the first sentence in the above paragraph. Volts times Amps is power. Power is not work, but is the rate at which work is done, or the rate at which energy is converted or transferred.

Power is represented by the symbol P. Power carries the units of watts (W). Electric Power, P, in watts (W) is defined as the electric potential difference, V, in volts (V) times the electric current, I, in amperes (A). Or P = V * I. Watts = volts * amperes. 1W = 1V * 1A.

Electric Energy is easily defined as power times time. Again electric work is same as electric energy and is equal to watts times seconds. Energy is often represented by the symbol W and carries the units of joules (J). [note: do not confuse the symbol W used as energy with the abbreviation W used for the unit of watt (unit for power)]

1V * 1A = 1W of power.
1W * 1s = 1J of energy.

A joule is equal to a watt second. Or in units, J=Ws. Not W/s.

A kilowatt hour is a measure or unit of energy equal to 3600000 Ws = 3600000J. 1kWhr = 1000W * 3600s = 3600000Ws = 3.6 MJ.

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The Joule is simply a universal unit of Energy equal to one Watt/second. That is one Watt of work performed for a time period of one second.
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"Watt/second" is an error. It is a "watt second". It is not watt per second. It is not power divided by time. "Per second" or "/s" implies a time rate, as in m/s meters per second (speed or the time rate distance is transversed. Energy is not a rate.

Power is a rate. Power is the rate at which work is done or the rate at which energy is converted or transferred. Power in watts is the rate of work or energy over time. Power(in watts) = energy(in joules) / time(in seconds). W = J/s. Or J = Ws.

But J does not = W/s. Since the watt (W) is a unit of power which is the rate of work (or rate of energy), a W/s implies acceleration of energy or J/s^2, joules per second squared, which is mostly nonsensical. The only place I've seen it appropriately used was describing how quickly a power generation station could come on-line.

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The concept of Energy applies to everything on every level, a Force is applied to something causing the something to move a Distance and Force x Distance equals Work. How much work is done over a given period of time is Energy.
...

Your last paragraph is good until you say this "How much work is done over a given period of time is Energy."

Leave out "over a given period of time" and it's ok.

Regards,
bi

[bistander]

Just saw this come across a news feed. Interesting, so I thought I'd share.

Quote from:

http://backreaction.blogspot.com/2020/10/what-is-energy-is-energy-conserved.html?m=1

What is Energy? Is Energy Conserved?
Why save energy if physics says energy is conserved anyway? Did Einstein really say that energy is not conserved? And what does energy have to do with time? This is what we will talk about today.



I looked up "energy" in the Encyclopedia Britannica and it told me that energy is "the capacity for doing work". Which brings up the question, what is work? The Encyclopedia says work is "a measure of energy transfer." That seems a little circular. And as if that wasn't enough, the Encyclopedia goes on to say, well, actually not all types of energy do work, and also energy is always associated with motion, which actually it is not because E equals m c squared. I hope you are sufficiently confused now to hear how to make sense of this.

A good illustration for energy conservation is a roller-coaster. At the starting point, it has only potential energy, that comes from gravity. As it rolls down, the gravitational potential energy is converted into kinetic energy, meaning that the roller-coaster speeds up. At the lowest point it moves the fastest. And as it climbs up again, it slows down because the kinetic energy is converted back into potential energy. If you neglect friction, energy conservation means the roller-coaster should have just exactly the right total energy to climb back up to the top where it started. In reality of course, friction cannot be neglected. This means the roller-coaster loses some energy into heating the rails or creating wind. But this energy is not destroyed. It is just no longer useful to move the roller coaster.

This simple example tells us two things right away. First, there are different types of energy, and they can be converted into each other. What is conserved is only the total of these energies. Second, some types of energy are more, others less useful to move things around.

But what really is this energy we are talking about? There was indeed a lot of confusion about this among physicists in the 19th century, but it was cleared up beautifully by Emmy Noether in 1915. Noether proved that if you have a system whose equations do no change in time then this system has a conserved quantity. Physicists would say, such a system has time-translation invariance. Energy is then by definition the quantity that is conserved in a system with time-translation invariance.

What does this mean? Time-translation invariance does not mean the system itself does not change in time. Even if the equations do not change in time, the solutions to these equations, which are what describe the system, usually will depend on time. Time-translation invariance just means that the change of the system depends only on the amount of time that passed since you started an experiment, but you could have started it at any moment and gotten the same result. Whether you fall off a roof at noon or a midnight, it will take the same time for you to hit the ground. That's what "time-translation invariance" means.

So, energy is conserved by definition, and Noether's theorem gives you a concrete mathematical procedure to derive what energy is. Okay, I admit it is a little more complicated, because if you have some quantity that is conserved, then any function of that quantity is also conserved. The missing ingredient is that energy times time has to have the dimension of Pla()nck's constant. Basically, it has to have the right units.

I know this sounds rather abstract and mathematical, but the relevant point is just that physicists have a way to define what energy is, and it's by definition conserved, which means it does not change in time. If you look at a simple system, for example that roller coaster, then the conserved energy is as usual the kinetic energy plus the potential energy. And if you add air molecules and the rails to the system, then their temperature would also add to the total, and so on.

But. If you look at a system with many small constituents, like air, then you will find that not all configurations of such a system are equally good at causing a macroscopic change, even if they have the same energy. A typical example would be setting fire to coal. The chemical bonds of the coal-molecules store a lot of energy. If you set fire to it, this causes a chain reaction between the coal and the oxygen in the air. In this reaction, energy from the chemical bonds is converted into kinetic energy of air molecules. This just means the air is warm, and since it's warm, it will rise. You can use this rising air to drive a turb(ain), which you can then use to, say, move a vehicle or feed it into the grid to create electricity.

But suppose you don't do anything with this energy, you just sit there and burn coal. This does not change anything about the total energy in the system, because that is conserved. The chemical energy of the coal is converted into kinetic energy of air molecules which distributes into the atmosphere. Same total energy. But now the energy is useless. You can no longer drive any turbine with it. What's the difference?

The difference between the two cases is entropy. In the first case, you have the energy packed into the coal and entropy is small. In the latter case, you have the energy distributed in the motion of air molecules, and in this case the entropy is large.

A system that has energy in a state of low entropy is one whose energy you can use to create macroscopic changes, for example driving that turbine. Physicists call this useful energy "free energy" and say it "does work". If the energy in a system is instead at high entropy, the energy is useless. Physicists then call it "heat" and heat cannot "do work". The important point is that while energy is conserved, free energy is not conserved.

So, if someone says you should "save energy" by switching off the light, they really mean you should "save free energy", because if you let the light on when you do not need it you convert useful free energy, from whatever is your source of electricity, into useless heat, that just warms the air in your room.

Okay, so we have seen that the total energy is by definition conserved, but that free energy is not conserved. Now what about the claim that Einstein actually told us energy is not conserved. That is correct. I know this sounds like a contradiction, but it's not. Here is why.

Remember that energy is defined by Noether's theorem, which says that energy is that quantity which is conserved if the system has a time-translation invariance, meaning, it does not really matter just at which moment you start an experiment.

But now remember, that Einstein's theory of general relativity tells us that the universe expands. And if the universe expands, it does matter when you start an experiment. And expanding universe is not time-translation invariant. So, Noether's theorem does not apply. Now, strictly speaking this does not mean that energy is not conserved in the expanding universe, it means that energy cannot be defined. However, you can take the thing you called energy when you thought the universe did not expand and ask what happens to it now that you know the universe does expand. And the answer is, well, it's just not conserved.

A good example for this is cosmological redshift. If you have light of a particular wavelength early in the universe, then the wave-length of this light will increase when the universe expands, because it stretches. But the wave-length of light is inversely proportional to the energy of the light. So if the wave-length of light increases with the expansion of the universe, then the energy decreases. Where does the energy go? It goes nowhere, it just is not conserved. No, it really isn't.

However, this non-conservation of energy in Einstein's theory of general relativity is a really tiny effect that for all practical purposes plays absolutely no role here on Earth. It is really something that becomes noticeable only if you look at the universe as a whole. So, it is technically correct that energy is not conserved in Einstein's theory of General Relativity. But this does not affect our earthly affairs.

In summary: The total energy of a system is conserved as long as you can neglect the expansion of the universe. However, the amount of useful energy, which is what physicists call "free energy," is in general not conserved because of entropy increase.

Thanks for watching, see you next week. And remember to switch off the light.

--- end quote.
Notice the definition of "free energy".

Enjoy,
bi

ps. Follow the link for video.

[lancaIV]

Walther Hermann Nernst
Josiah Willard Gibbs
Carl Friedrich von Weizsaecker
and each  them their ' energy '- definition I would recommend !
Sincerely

[onepower]

Bistander

I disagree. The standard definition is that energy is equal to work, not work times time. You often see the equation E = Ws which is saying that energy (E) = power (W) * seconds (s).

Wikipedia-
The work W done by a constant force of magnitude F on a point that moves a displacement s in a straight line in the direction of the force is the product.
W=Fs

It depends on our perspective, Work = force x distance, the electric field produces a force on an electron causing it to move a distance, is this not work by definition?.

Work is not represented by the symbol W. Work is energy and carries the units of joules. A joule is equal to a watt second. 1J = 1W * 1s = 1Ws.

If work is energy then why not use one term instead of two?. Obviously work is not energy because they have different definitions and the context matters.

Work is equal to force times distance. Work in joules = force in newtons times distance in meters. Since work is energy, it is represented by the symbol E. So E (joules) = F (newtons) * d (meters). 1J = 1N * 1m. Joule = Newton meter.

So if one newton of force acted on an electron causing it to move one meter (one newton meter) is it work, power or energy?. There was an electric "force" measured in volts and it caused an electron to move a "distance" which we measured as a current, is that not work?. 

I get what your saying and I know how to do all the calculations I just choose not to because it's kind of pointless. So I purposely changed the context to make people think which obviously didn't work. You see if we could exist on the atomic scale watching particles move around like planets most of the terminology becomes a mute point. You could say, oh that's just a current as an electron the size of the moon zips past. Then I would say, so the best description you have for a massive body zipping by near the speed of light is a current or some simplified equation?.

I think this is the reason so many fail in free energy because there perspective is skewed and subjective. They say that object is just an object but in reality it's 1% particle/fields and 99% space full of EM waves. They also think common objects have no energy despite the fact that if we could liberate "all the energy" in something like an apple it could incinerate a large city. We seem to keep describing stuff as something we know they are inherently not for some strange reason.

I would submit most of the language and equations most use to describe nature and natural phenomena are basically a joke because it doesn't really describe anything. Which is why so many people seem so confused by the term energy. Regardless of the terminology only a change in force can cause a change in motion and the change in motion represents energy on every level we know of. As Einstein said- "nothing happens until something moves".

Regards