Electromagnetic physics question

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Chris Smith
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Re: Electromagnetic physics question

SOME of Tesla’s Inventions, pioneering, and Studies include......<p>The radio
Remote control
AC poly Phase motors
AC electricity
Transformers [Tesla coil is a Transformer]
MRI
Tank circuitry and harmonics<p>Just to name a few, and most are 100 years old by now. <p>Excerpts from one of the many web pages on Tesla [http://www.apc.net/bturner/tesla.htm]<p>The AC motor and Transmissions<p>Tesla's main claim to fame lay with his invention of the alternating current motor. Tesla believed that alternating current was vastly superior to (Edison's) direct current, but the problem was the lack of a practical motor. Alternating current is practical because of the fact that it can be altered or converted to suit a variety of situations. For example, if the voltage is made quite high, then the current necessary for a specific level of power is very low. This low current then becomes very efficient when sending electrical power over very long wires. (This is the reason why the power lines running across the countryside are at very high voltages.)<p>

rshayes
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Re: Electromagnetic physics question

The DC line on the Pacific Intertie can carry 3100 megawatts. One wire is at +400 KV, the other one is at -400 KV. The total voltage is 800 KV. The current capacity of the line is thus 3875 amperes. If operated as an AC line, the peak voltage would be limited to 800 KV by the insulators and ground clearance. This is an RMS voltage of 566 KV. The current rating would be approximately the same, assuming the skin effect is insignificant at 60 Hz. The AC power capacity would be 2193 megawatts. By operating the line on DC the capacity of the line has been increased by 907 megawatts.<p>The same current is flowing through approximately the same resistance. The losses due to series resistance are equal. The DC line is transmitting more power with the same losses. Hence it is more efficient.<p>With short lines, the additional costs of the rectifiers and inverters required for the DC line are more than the cost of a higher power line. The additional terminal costs of a DC line are independent of the line length. As the line is made longer the cost of the line increases, and eventually exceeds the costs for the DC conversion equipment. At this point, the DC line becomes worthwhile.

dyarker
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Re: Electromagnetic physics question

I figure AC coming out at better than 3200MW. (3 phase not one)((like 6000MW??)) Right-of-way and towers cost a lot more than the third wire.<p>And, we've probably lost Ian along the way!<p>Efficiency is everything. Move the most for the least cost with least lost.<p>no_vice, the twisted pair isn't part of the metal detector circuit, and it's about the same amount of metal twisted, or not.<p>[ December 22, 2004: Message edited by: Dale Y ]</p>
Dale Y

jwax
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Re: Electromagnetic physics question

steven, apples and oranges. The DC system was designed for DC. Had it been designed and built for AC, the insulation would have been appropriate for AC, and efficiency is not involved. On their website, ABB says the advantages of the HVDC system over an AC system is "long distance, and stability". No mention of efficiency. A watt is still a watt.
BTW, they just upped the operating voltage to +/- 500 KV.

rshayes
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Re: Electromagnetic physics question

Chris Smith
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Re: Electromagnetic physics question

If your getting your total history from the reading of patents, again you coming up short, and hence your ignorance in many fields. Tesla was the inventor of radio, and it doesn’t get any simpler that that. Not only was he ahead of the whole game, and almost every scientist and physicist of the day, but half his theories and inventions were never realized for another 50 years, by other duplicating his ideas in a age when material goods made them possible.

You book of history must be easy reading, as short as it is.<p> But keep rooting for Edison, he needs all he can get, because he knew close to nothing about electricity, light bulbs, and most of the other things his slave workers invented, as he took out patent after patent, and profit as well.

MrAl
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Re: Electromagnetic physics question

Hi there,<p>Stephen:
Im sorry but i dont think you're correct on
your efficiency calculations because of your
assumptions about how an AC line vs a DC line
are rated in terms of voltage.<p>When a line is rated it can be for both ac and
dc, and for ac RMS voltage is used.<p>For example, a DC line that can support
300kv DC can also support an AC line of 300kv AC
RMS, not PEAK as you had assumed. This makes the
two pretty much equal in that respect.<p>There are various reasons for using DC over
AC or vice versa, but none of them are voltage
related.
For example, there is a physical limitation on
the length of an AC line while none on DC, so
someone might chose to use DC because the line
is going to have to be extremely long. Again,
however, it's not because the DC line is more
efficient.
Another example is where two grids will be
joined by a line where there is something about
each grid that is different, which would require
power conversion anyway.<p>Take care,
Al
LEDs vs Bulbs, LEDs are winning.

rshayes
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Re: Electromagnetic physics question

There must be thousands of web sites with pages on Tesla that state the the Supreme Court voided Marconi's basic radio patent and awarded it to Tesla in 1943. Being ignorant, I went to some of the legal sites, found the case, and read it. Basically, the tale is false. The Supreme Court did no such thing. It voided one of the later Marconi patents on the grounds that the claim in Marconi's patent was anticipated by an earlier inventor. The inventor was named Stone, not Tesla. There was no transfer or award of the patent, it was simply voided. The previous patents by Marconi were not affected.<p>If anyone invented radio, it would have to be Maxwell or Hertz, or possibly both as coinventors.

Bernius1
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Re: Electromagnetic physics question

Something awry. A truck starter consumes about 1800 amps when initially starting up. 4 batteries thru 00-gauge cable, 4 of 5 feet long. Anyone who knows heavy-duty battery theory & wiring knows that wire gauge and even slight corrosion resistance will greatly reduce net amperage at the motor ( which behaves as a dead short initially). So power transmission lines, even at very high voltages would need to be large and corrosion-free.
Now, Re: AC, if you touch a downed wire, even without holding your water-supply pipe, you'll still be sufficiently grounded to be injured. Why ? Does the ground REALLY conduct ? Ha. Minimally. But because it's AC and you & the ground DON'T conduct, you're acting as a large capacitor ( farads, I don't know),which charges you ~80V peak one way, & then ~170V the other way. Granted, if the resistance drops low enough ( note, not reactance ), then enough actual current will flow to kill, but the reactance has more to do with a shock felt in an incomplete circuit. BTW, what are the spec's for human skin resistance ? Now multiply that into 5'11",(because it flows over the skin), and through shoes.
So, if I'm right , then my house acts as a big capacitor, receiving a 10kW , 60Hz, hard-wired signal.
BTW, if your neutral is loosed from the water pipe, will you get NO voltge, or just LOW voltage ?
HMMMMMmmmmmm......
Can't we end all posts with a comical quip?

jwax
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Re: Electromagnetic physics question

I'm making an early New Years resolution-stop participating in this pointless thread.

rshayes
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Re: Electromagnetic physics question

perfectbite
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Re: Electromagnetic physics question

Stephen,
You mentioned two things:<p>"Edison applied himself to a wider range of devices than Tesla, for example the light bulb, batteries, telephone and phonograph. He also observed the "Edison effect" in a light bulb. This was the basis for the Fleming valve, which was later developed by De Forest into the vacuum tube. That was the big fish that got away for Edison."<p>What was/is the "Edison effect"? Quite a while ago a posting to the forum asked about the 'blackening' that occurred in light bulbs. Are these phenomena related? and,<p>I too would be mind boggled by a 1,000 mile long lighting bolt continually coursing through the high atmosphere (Would that create or delete (negate) ozone?) and, if it were brilliant enough we wouldn't need street lighting at night (there would go our diurnal rythm) but children born and raised under such a light show would not have boggled minds
and,<p>perhaps Mr. N. Tesla should be canonized by the Temple of Science and be called the 'new' Saint Nicholas who's catch phrase, instead of Ho, Ho, Ho. would be Hum, Hum, Hummmmmmmmm. or at least have his birthday honoured (I don't see why not, Mozart and Wagner et al have their birthdays celebrated). Zeus already has a lightning bolt and Arachne already has a threadlike spool but perhaps Tesla's symbol could be a caduceus like staff with intertwined lightning bolts (representing AC of course) instead of snakes?<p>[ December 23, 2004: Message edited by: perfectbite ]</p>

Chris Smith
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Re: Electromagnetic physics question

The Supreme Court case was Marconi Wireless v. US, 320 US 1 (1943). There were three dissents to the opinion. <p>Your getting closer? <p>But your still out by quite a few decades.

Ron H
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Re: Electromagnetic physics question

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by jwax:
steven, apples and oranges. The DC system was designed for DC. Had it been designed and built for AC, the insulation would have been appropriate for AC, and efficiency is not involved. On their website, ABB says the advantages of the HVDC system over an AC system is "long distance, and stability". No mention of efficiency. A watt is still a watt.
BTW, they just upped the operating voltage to +/- 500 KV.
<hr></blockquote>
You have to hunt for it, but there is definitely a mention of <p>efficiency.
BTW, skin depth at 60Hz is about 8mm, probably a lot less than most electronics types would guess.<p>[ December 23, 2004: Message edited by: RonH ]</p>

Ron H
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Re: Electromagnetic physics question

Oops! Sorry for the double post.<p>[ December 23, 2004: Message edited by: RonH ]</p>

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