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Old 22-12-2010, 14:05   #1
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Electrons, Electricity and Energy

I'm trying to understand what is the source of energy at the point of a load that is used to do work.


As I understand it the battery “pushes” the electrons through the circuit. The electrons go through the circuit from one end to the other. The electrons are negatively charged but they retain that charge. So this charge is not consumed.


I then wondered whether it is the movement of the electrons through the circuit that provides the “energy” to do work? I understand that the “pressure” that the battery applies is used up, in that there is 12 volts at one end and zero at the other and that that pressure moves the electrons through the circuit. But it can't be the movement of the electrons because that movement or momentum would basically cease to exist past the load after it had been used up by the load and that's not the case because the electrons come out the other end.


In order to do work, some form of energy is used up. This is, I assume from what I've read, is electric energy. Which is a term used in the book “The 12 volt Bible”. But I still don't know what is this energy that is used and, by definition, consumed at the load.


Is there anybody who knows the answer and who can explain it in an “idiot's” guide kind of way?
Please and thanks.
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Old 22-12-2010, 14:14   #2
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The simple, common analogy is to compare electricity to water.

The water pressure or psi (pounds per square inch) is comparable to voltage in a battery. Higher water pressure is more powerful, higher voltage likewise.

The water moving through a pipe is like the electrons moving through the wire so amps.

The amount of water that moves through a pipe in a certain time is like the watts or total power produced.

So, one example. You want to use water power to do some work like spin a turbine to generate electricity. This is comparable to using electrons to spin a motor to do some kind of work, like hoist an anchor.

Obviously the water moves through the turbine and does work, it doesn't get to the turbine and stop. The turbine will transfer some of the kinetic energy of the water to the generator and convert that energy into electricity.

Likewise the electrons go to the windings of a motor, turn the motor and some of the energy in the electrons is converted into rotational force in the motor to hoist your anchor.

The analogy can go further if you like.

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Old 22-12-2010, 15:00   #3
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In your battery, chemical energy that was "waiting around", doing nothing much but "sitting" in the battery being potential, suddenly starts turning into electrical energy. The new electrical energy, formerly known as chemical, zips through some machine/device to perform work. Now the energy that used to be electrical has become the mechanical energy of the machine.

Energy is generally defined as the capacity for doing work. Power is the rate of doing work, or the rate of using energy:
P = Work/t = Energy/t
where t is time

By definition, work done by a constant force F, when it moves an object by distance L in the direction of force is:
Work=F×L

We know that in an uniform electric field, with voltage V over distance L, the force acting on a charge Q is equal to F=V/L×Q. (Particularly, in the field of 1 volt/meter, force of 1 newton is acting on one coulomb charge).

Substituting this into the above general expression of work gives the equation for P required to move a charge Q in an electric field: P = F×L/t = V×Q/t. The rate of charge flow Q/t is called electric current I. Replacing Q/t with I in the above formula yields a familiar expression for instantaneous value of electrical power: P=V×I. In AC circuits voltage and current are often shifted in phase and are not sinusoidal. In such cases the quantity volt-amps describes the apparent power.

Richard Feynman, one of the best known physicists of the twentieth century said, "It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount".

Here's another one from a guy named David Rose (MIT engineering professor famous for his work in fusion, energy, and nuclear engineering): "Energy is an abstract concept invented by physical scientists in the nineteenth century to describe quantitatively a wide variety of natural phenomena".

Now do you understand? If so, please explain it to me.

See also
Electronics For Dummies - Google Books

If you found the above illuminating, I'd ask you to pay it forward by explaining "the meaning of life", for me.

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Old 22-12-2010, 15:15   #4
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energy delivered to a "point" load

The energy delivered to a load is dependent upon the number of electrons that pass through the load, period. The load may utilize the energy as heat directly or by extracting the energy from the magnetic field created by electron movement indirectly. Ultimately all energy extracted from the electron flow is converted to a form of work or heat or photons. Heat may be viewed as photon energy in the lower end of the electromagnetic spectrum.
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Old 22-12-2010, 15:28   #5
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Energy is neither created or destoryed, only changed in form. All energy we have now we have always had in some other form.

Energy "flows" from a high energy to a lower energy.

Batteries are stored chemical energy. If connected to a "load" of lower energy the chemical energy converts to an electrical energy to flow to the load. The load comsumes the electrical energy to do "something" and in the end is converted to heat or some other stored energy (like a fluid energy if by water pressure).

In thermodynamics you can always to an energy balance to find what it becomes. But all that starts the process equals the end. Even "lost" energy still exists, but normally has been converted to heat (that's where effieciency loss goes).

PS - I'm ex-Navy so I learned electrical as electronic flow, but the rest of the world learns it as hole flow.
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Old 22-12-2010, 15:43   #6
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It has been proven, time and time again, that there are no such thing as electrons.
All wiring is filled with smoke. Smoke goes round in circles, somewhat like steam being condensed and revaporized.
When the wire get a hole, smoke comes out, and everything stops.
This discovery has been confirmed by any user of Lucas components.
Ask any owner of a 60's British sports car.
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Old 22-12-2010, 16:18   #7
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... PS - I'm ex-Navy so I learned electrical as electronic flow, but the rest of the world learns it as hole flow.
"Hole flow"
Would it be fair to assume that you first studied the subject in the 1960s, as I did?
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Old 22-12-2010, 16:24   #8
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It has been proven, time and time again, that there are no such thing as electrons.
All wiring is filled with smoke. Smoke goes round in circles, somewhat like steam being condensed and revaporized.
When the wire get a hole, smoke comes out, and everything stops.
This discovery has been confirmed by any user of Lucas components.
Ask any owner of a 60's British sports car.
Manufacturers put a little bit of magic smoke (also called factory smoke or blue smoke) into every electronic component; and it is this smoke which makes the device work. Once the magic smoke has been released, usually when overheated, often through exposure to an extreme electrical current, usually caused by the application of excess voltage through some failure of the circuit, the device lacks its key component and no longer works. The smoke can thus be thought of as an essential part in the device's function, and once let out, the magic smoke cannot be put back in.
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Old 22-12-2010, 16:24   #9
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Quote:
Originally Posted by Blue Stocking View Post
It has been proven, time and time again, that there are no such thing as electrons.
All wiring is filled with smoke. Smoke goes round in circles, somewhat like steam being condensed and revaporized.
When the wire get a hole, smoke comes out, and everything stops.
This discovery has been confirmed by any user of Lucas components.
Ask any owner of a 60's British sports car.

If I cast my mind back 30 years to when I owned a Mini, I can identify with your frustrations.
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Old 22-12-2010, 16:38   #10
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I'm reminded of a story I heard once which is probably completely false but illustrates the point very well.

A rather monotonous, stuffy old professor was giving a lecture on electricity when he noticed that one of his students was dozing off. Being old school, in more than one sense of the phrase, he fired a piece of chalk at said student in order to get his attention. "Mr Smith", he said, "Can you please explain to the class how electricity works?" Mr Smith, in a fatal attempt to save his dignity, replied, "I seem to have forgotten, Sir". Upon which the professor paused and said, "There, ladies and gentlemen, is one of the great tragedies of our time. Only two beings in the Universe know how electricity works; God and Mr. Smith. God isn't telling and Mr. Smith has forgotten." With that, the professor gathered his belongings and left the lecture hall.
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Old 22-12-2010, 16:40   #11
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If I cast my mind back 30 years to when I owned a Mini, I can identify with your frustrations.
Aaaahhhh!! the"prince of darkness" has broken many a lovely's heart.
Had the first CooperS in Bermuda in 1965.
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Old 22-12-2010, 16:41   #12
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Quote:
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Energy is neither created or destoryed, only changed in form. All energy we have now we have always had in some other form.

Energy "flows" from a high energy to a lower energy.

Batteries are stored chemical energy. If connected to a "load" of lower energy the chemical energy converts to an electrical energy to flow to the load. The load comsumes the electrical energy to do "something" and in the end is converted to heat or some other stored energy (like a fluid energy if by water pressure).....
Thank you all for the replies. I did understand that energy can't be destroyed and also, separately, that all electrical books and articles that I've read are very fond of water analogies. But it is this "electrical energy" that Don refers to that the electrons, presumably, are "carrying" that I was trying to understand.
My partner gives out to me that I always want to know why something does what it does. Driving the boat in reverse, she knows turn the wheel to one direction and the boat will go in that direction (prop walk, wind and current allowing), whereas I can only do it when I've figured out how the wheel turns the rudder, how the water hits the rudder and.... oh sh~~ i've crashed...
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Old 22-12-2010, 17:26   #13
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Even though I took a shot at it for you; since I'm really a mechanical engineer I also normally kind of think of the electrons as water, the wires as pipes, the battery as a pump. If that also works for you go with it. In the end its all really just PFM..............(pure f*****g magic).

PS - we pretty much know how electricty works. But the magnetsim it is based on is a different matter.
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Old 22-12-2010, 17:44   #14
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...But it is this "electrical energy" that Don refers to that the electrons, presumably, are "carrying" that I was trying to understand.
I'll try to help out with a simplified version of my class. When I teach electron theory to my students I start with a basic lesson on atoms. You have neutrons and protons in the middle, and electrons "orbiting" around them. Neutrons have a neutral charge, and protons have a positive charge. Finally, electrons have a negative charge. The free electrons move from atom to atom. This movement of negatively charged "free" electrons is the energy your looking for. Ok, here comes the hard part for most: Since it is the negatively charged electrons that are moving, modern theory is that electricity flows from negative to positive. (this is why "grounds" are sooo important) Hope that helps, and I didn't leave out too much.

Wow, that was harder to type than it is to talk about....wheres my dry erase marker???
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Old 22-12-2010, 17:44   #15
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Hey Don, when you get a few minutes, give us a quick explanation of why gravity exists--and what is it?
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