Posted on 07/29/2005 2:28:26 PM PDT by Grendel9
When you say "interesting interpretation", which of the numerous things I mention are you talking about?
When I mentioned energy, I was talking about energy delivered to the customers. 'Consumed' in the layman's terms but converted, as I mentioned, in more scientific terms.
You used the term 'power to be produced'. That terminology is where I have the problem. I would say energy is produced (converted) at a certain rate. You can think of 'using' power, but the only way you can purchase it is by measuring how long you use it. That is why the electric bill mentions the number of kWh you use. They could send you a graph of the instantaneous power versus time and show you the area under the curve, along with you peak power, but they can't charge you for power alone. Instantaneous power is interesting since we can 'see' what is going on and it does measure the stress on the delivery infrastructure, but energy delivered, (the area under the curve) is what we buy.
As far as being more impressed by current or current density, since current density is current divided by area, there are several ways to increase it. If we are looking at the main transmission line alone, the area of it will remain roughly constant, so quadrupling the current will quadruple the current density. I am equally impressed.
When someone proclaims a new power record, the public does not realize what it means. They don't realize that that record may have existed only for a few minutes. It does not necessarily mean record energy production (conversion) for the day. That is where the media lack of understanding distorts reality.
I am glad Maxwell's equations are helpful to you but they don't help the average guy trying to figure out the difference between power and energy.
Yes, I am a big fan of Bill Beatty. He is not afraid to shake things up. The most important thing he says is that terminology is important. This is especially true when teachin. We so easily toss around terms such as current, power, energy that the kids have no real concept of yet. One of his pet peeves is to say that current flows. Sounds good to most of us since we understand what it means. But to a kid, there is this thing called 'current' and if 'flows' in wires. Sort of like 'water' that 'flows' in a river. Then we mention 'charge' and tell them that 'flows' in the wire. Oh, so charge IS current since they both flow?? That's what it sounds like to them. That is when they shut down since the language is not consistent.
I make sure to always say 'charge flows' and 'there is a current in the wire'. Just as we would say 'water flows' and 'there is a current in the river'. Sounds picky to us, but the kids appreciate the consistent use of the language.
I like these quotes:
"Lest you think that I am quibbling over minor points of language, I note that in my experience many of the misconceptions people harbor have their origins in imprecise language... Precise language is needed in science, not to please pedants but to avoid absorbing nonsense that will take years, if ever, to purge from our minds."
- Dr. Craig F. Bohren, from his "Clouds in a Glass of Beer:
Simple experiments in atmospheric physics"
"(language) becomes ugly and inaccurate because our thoughts are foolish, but the slovenliness of our language makes it easier for us to have foolish thoughts." - George Orwell
"The search for the MOT JUSTE is not a pedantic fad but a vital necessity. Words are our precision tools. Imprecision engenders ambiguity and hours are wasted in removing verbal misunderstandings before the argument of substance can begin." - ANONYMOUS CIVIL SERVANT (from Roget's Thesaurus Webpage)
"Many errors, of a truth, consist merely in the application of the wrong names of things." -Spinoza
The current travels on the surface of the conductor rather than the cross-sectional area. Current density is closer to the measurable phenomenon. You might enjoy of good series in the Philosophy of science, studying the etymology of the terms used to express physical phenomenon and their historical progress in differential math.
The Poynting Vector might provide better insight, after one memorizes Maxwell's Eqns in differential and integral format.
". . .said they generated a current equal to roughly four times all the electrical power on Earth."
Actually, this kind of current has been generated before when I accidentally scraped the tinfoil on a gum wrapper across my silver filling.
It still wouldn't run my notebook computer for more than two hours.
Not usually. I know there is such a thing as the skin effect, but that applies not to DC or low frequency AC but to high frequency AC. DC current travels through the whole conductor, otherwise, instead of using big fat jumper cables, we could use a plastic hose with a thin coating of copper. I would suggest making such jumper cables and trying them out! Wear goggles since the copper will probably evaporate in a flash. Even for 60 Hz AC the skin effect is minimal. I know some transmission cable has a non-copper core, but this is for strength. Assuming 60 Hz transmission, skin effect is small. Yes, for high frequency signals, you CAN use hollow copper pipes.
You might enjoy of good series in the Philosophy of science, studying the etymology of the terms used to express physical phenomenon and their historical progress in differential math.
I had some of those courses years ago while I was majoring in physics. Teaching high school, I don't really get to stay in touch, even in the AP class, although we do uses diffeq for air resistance, and charging and discharging of capacitors. We do look at Maxwell's in terms of diffeq but really don't get deeper than that since it is an intro class.
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