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#31 |
Superior Inhabitant
Join Date: Sep 2002
Posts: 74
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Electricity is an electromagnetic wave. There is an electrically charged component, and a magnetic component. The moving electrons induce a magnetic field, and the changing magnetic field induces an electric field, and this effect propogates energy through whatever medium is being used.
Now if you put something conductive near this electromagnetic field surrounding the power lines, part of the magnetic field that would have been inducing current into the power lines instead induces electric fields into the conductor, in this case flourescent bulbs. So the main conductor, the power line, has energy bled off of it. The flourescent bulbs then turn that induced current into light. However, if there were nowhere for the energy to go, the electromagnetic field induced into an external object would be stored and returned to the power line when the current reverses direction, (60 times every seconds in the U.S., 50 in England). So in that case the energy isn't lost, it gets fed back into the power line. However, this effect does through the voltage and current out of sync with each other, which does bad things for efficiency if you don't correct for the problem by pushing them back in sync again. This induction effect also means that we wouldn't get 100% efficient energy transfer by changing our power lines to superconductors. I once read that the main power line losses are through induction, not resistance, so even though superconductors have no resistance, we wouldn't really gain much savings by switching to them. Hopefully this explanation wasn't too confusing to those who haven't studied physics/electrical engineering, and not too inaccurate for those who have ![]() |
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#32 |
The future is unwritten
Join Date: Oct 2002
Posts: 71,105
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Thanks linknoid, so the power that leaves the generation plant on the high tension lines, divides into two components for the journey. one is the electricity in/on the wire and the other the electromagnetic field surrounding the wire? Rather than the electromagnetic field being created out of thin air, as a side effect, of 100% of the power transmitted along the line?
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#33 | |
King Of Wishful Thinking
Join Date: Jan 2001
Location: Philadelphia Suburbs
Posts: 6,669
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Quote:
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Exercise your rights and remember your obligations - VOTE!I have always believed that hope is that stubborn thing inside us that insists, despite all the evidence to the contrary, that something better awaits us so long as we have the courage to keep reaching, to keep working, to keep fighting. -- Barack Hussein Obama |
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#34 |
“Hypocrisy: prejudice with a halo”
Join Date: Mar 2007
Location: Savannah, Georgia
Posts: 21,393
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Interesting, electricity is a simple concept with lots of variables. But let me ask, is the 'energy bled off" the high tension lines actually lost energy or merely a by-product of the movement of the electrons with no loss in total power? I always understood it to be the later.
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#35 |
Greener than the rest
Join Date: Apr 2007
Location: Near London
Posts: 68
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I believe it to be a by product, as that high power eletricity will cause a change in a magnetic field, so unless you do something major to disrupt that magnetic field there would be no total loss in power. This is based on the physics that I can remember from a few years ago, so please correct me if Im wrong
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#36 |
A serene breakdown
Join Date: Dec 2005
Location: Northern NJ, USA
Posts: 266
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If the tubes are giving off energy in the form of light, that energy has to be coming from the lines. It is simply conservation of energy.
But 1301 tubes times 25 watts (or so) is pretty small compared to the many many megawatts going overhead. [I used to teach undergrad physics]
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#37 | |
“Hypocrisy: prejudice with a halo”
Join Date: Mar 2007
Location: Savannah, Georgia
Posts: 21,393
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Quote:
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#38 |
Professor
Join Date: Oct 2006
Posts: 1,911
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There is no proof living under lines causes any medical problems. You need much higher levels as found in the air-gap of motors not under high tension wires.
linknoid; You are correct in the loss area BUT! There is a lot of energy lost to heat along those cables. They actually control the current thru the cables as related to this heat. In the long term they want to run them below 600F because the wire will anneal and weaken greatly. In the short term all transmission lines are designed so that at the maximum expected loading, on a hot day, they don't sag below a certain ground clearance. Many blackouts occur because the line is over loaded in hot, still weather, and the lines sag into trees. A lot is lost thru induction via fences and metal structures. That's usually hard to prevent and in fact necessary as large metal structures that are under the lines and not grounded can pose a "touch hazard". So in grounding them the energy escapes to the earth. Just don't let the power company find you using any of this. A farmer noticed that he'd get jolted touch his new fence in hot dry weather. (Poor grounding in dry soil.) He decided to hook his fence to a load. Then wasn't enough so modified his fence to better isolate it. Then he added to it to increase the "reception". They figured it out and he was taken to court.. I guess they take that as energy stealing. If you look at fences around substations and under transmission lines you can find often find grounding rods tied to them. |
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#39 | |
Superior Inhabitant
Join Date: Sep 2002
Posts: 74
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Quote:
Think of the electectromagnetic waves like waves in the ocean. It's just an analogy to illustrate a point. The waves themselves are not the water itself, the waves are the motion of the water. The water itself is just the medium that is transferring the energy. It's the same way with electricity, the electrons are acting as the medium to guide the electromagnetic radiation. Now in more detail. Imagine an electron sitting there, minding its own business. It has a negative charge, and suddenly along comes an electrical charge that starts pushing it. The energy that goes into the electron weakens the wave, because that energy was transferred to the electron in the form of motion. When an electron is accellerating, it generates a magnetic field, and a changing magnetic field causes other electrons to accelerate, releasing energy from the electron into the surrounding ones, so it decelerates. But now there are more electrons in the "ahead" direction than the "behind" direction, creating an electric field which causes the electrons in front of the wave to be pushed "forward", and the electrons behind to be "pulled" by the now positively charged area in front of them. And the energy propogates. So now you have these expanding and collapsing waves of magnetism and electric charge. These waves reach far outside the confines of where the electrons are moving, it's just there are no free electrons to play along outside the conductor. If you put another conductor next to that one, the changing magnetic fields will make the electrons in this new conductor move in the same way, they're absorbing energy from that electromagnetic wave. In fact, if you make the waves strong enough, and you have a something to conduct that electricity just right, you can induce these waves into the other conductor over incredible distances. This discovery led to the invention of the radio, and all the subsequent inventions based on it. Radios are designed to strongly amplify these waves at 1 frequency, and cancel out all the other frequencies. In an AM radio, the sound you here is transmitted by changing the strength of the wave over time (AM is short for Amplitude Modulation, which means it "modulates" the signal using the amplitude of the waves). Metals tend to have a lot of electrons that are loosly bound, that are free to move around in response to voltages. Other materials tend to hold onto their electrons more closely, so they don't respond to the EM waves as effectively, and when they are forced to by a strong enough voltage, they tend to move in a much less organized manner and convert a lot more of the energy into heat. However, these waves can travel even without having electrons around to carry them. How that is, I'm not really sure, but they can propogate on their own in complete vacuum. So what are these waves in? They are waves in nothing, that just happen to interact with all these electrically charged particles everything is made of when they get close. I hope that all made sense. |
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#40 |
The future is unwritten
Join Date: Oct 2002
Posts: 71,105
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Yes, very much so. Thanks for taking the time to explain that.
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