Electromagnetic physics question

[Chris Smith]

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]
Radar Theory
Radar parts Design
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>
Radio<p>Tesla also worked with radio-frequency electromagnetic waves, and despite the claims made by Marconi, actually did invent the idea of Radio as we know it today. (There are numerous patents which bear this out.) <p>Turbines<p>Tesla was also a great mechanical engineer, and patented dozens of devices ranging from speedometers to extremely efficient electrical generators. One unique device was his bladeless turbine. Instead of using fan-type blades, Tesla's turbine utilized solid disks of metal, and relied on what is called the 'boundry-layer effect'. His turbine ran on either compressed air or steam, and was so efficient that a device held in the hand could produce well over 10 horsepower! Today, this bladeless technology is being used in a special type of non-clogging pump designed for the oil industry. (In fact, the thicker the stuff it pumps, the more efficiently it pumps it!)<p>Radar and MRI<p>Tesla was also responsible for a great many other inventions and devices that we take for granted today. He postulated the ability to locate objects in the air or in the ground by using radio waves. Today, we call it RADAR, and when used to peer into the human body, MRI. Tesla also created radio- control devices. His work with special gas-filled lamps set the stage for the creation of fluorescent lighting.<p>There still are no advantages to DC, otherwise Greed, profit, and the market place would have won out, long, long, long time ago.

[rshayes]

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]

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>

[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.

[rshayes]

The Supreme Court case was Marconi Wireless v. US, 320 US 1 (1943). There were three dissents to the opinion. Neither the opinion or the dissenting opinions declared that Tesla was the inventor of radio. The decision is about 80 pages long. Tesla in mentioned only a few times in the text and in a couple of footnotes. The issue was the validity of a single claim in patent no. 763,772 which had been filed by Marconi in 1900 and issued in 1904. This claim was for a radio system using four tuned circuits, all tunable to the same frequency. An inventor named Stone was found to have previously invented this arrangement and that the Marconi patent was invalid. There was no award of a patent to Tesla.<p>This web site (9www.luminet.net/~wenonah/new/tesla.htm) has a list of 111 US patents granted to Tesla. Of these, 11 are identified as "radio" patents.<p>Three of these (645576, 649721, and 1119732) describe his proposed wireless power transmission system. The first two refer to the transmission of power by using high voltage to create a conductive path in rarified air. There are references to a Crookes tube, and he is clearly describing ionic conduction (either a glow discharge or an arc) and not radio waves. The second patent specifically states that he is not using Hertzian waves. The last patent describes the construction of the tower that he eventually built on Long Island.<p>A single patent (613809) describes his remote controlled boat. This patent does not show any attempt to provide a resonant circuit in either the transmitter or receiver. The use of resonant circuits for generating radio waves and increasing the sensitivity of the receiver was known to Hertz at least 10 years before and was used by others subsequently. The transmitter was only vaguely described, and appears to have been based on discharging a capacitor into a step up transformer to generate a short high voltage pulse rather than a radio wave.<p>A sequence of four patents (685953, 685954, 685955, and 685956) describe devices for detecting electrical "disturbances" with improved sensitivity. He cites several "old" methods of creating "disturbances", one of which is Hertzian waves. To these methods, he adds his preferred method, which is to inject a current into the earth which is then conducted to the receiving station through the ground. He does not describe any apparatus for generating hertzian waves and the detection method shown would probably not detect them. The basic idea was that of a synchronous rectifier followed by an integrator.<p>One patent (787412) describes the resonant excitation of the earth. Again, he talks about energy being conducted through the ground, not radiated through space. This is not too suprising, since the discovery of the reflecting layers in the atmosphere was over a decade away.<p>Two patents (723188 and 725605) describe a system for transmitting and receiving on two frequencies simultaneously. The two channels were combined so that both were needed to indicate that a signal was present. These are the only patents of the "radio" group to actually show deliberate tuning of the transmitting and receiving circuits.<p>In several of these patents Tesla refers to Hertzian waves as too weak to transmit the power that he wanted to. His primary methods were based either on conduction through the ground or conduction through the atmosphere via an ionized path. None of these "radio" patents disclose anything involving radio that was not well known.<p>The MRI claim is totally ridiculous. MRI (Magnetic Resonance Imaging) is based on an effect called Nuclear Magnetic Resonance (NMR), wihch was discovered in 1946, about three years after Tesla's death. These machines use superconducting magnets. Superconductivity in Niobium-Tin (used in MRI magnets)was not discovered until 1954.

[Chris Smith]

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]

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

[rshayes]

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.
James Maxwell used the results of earlier researchers to formulate a series of equations which described their results in a consistent manner. One of the solutions to these equations describes radio waves. Heinrich Hertz built the first apparatus for generating and receiving these waves, and demonstrated their properties. This was done and reported in the scientific literature about a decade before Tesla's experiments. Marconi's starting point was Hertz's work.<p>One of the Tesla pages had a list of his US patents. Of these, 11 were classified as "radio" patents. Since I was ignorant, I went to the patent office web site and downloaded copies. His "remotely controlled boat" patent (613,809) does not mention radio waves and shows transmission and reception apparatus that is cruder than that used by Hertz over 10 years before. This is in a document prepared and signed by the inventor which describes the "preferred embodiment" of the invention. Another of the patents (649,621) describes his method for transmitting energy through "natural media". It specifically denies that this is to be done with radio waves. On page 3, line 72 he states, "It is to be noted that the phenomenon here involved in the transmission of electrical energy is one of true conduction and is not to be confounded with the phenomena of electrical radiation which have heretofore been observed and which from the very nature and mode of propagation would render practically impossible the transmission of any appreciable amount of energy to such distances as are of practical importance". Other patents in this group of "radio" patents mention radio waves, but describe other methods as preferable to radio waves. From this I would conclude that Tesla had little actual interest in radio, since he felt that it was inadequate for the transmission of electric power, which seems to have been his primary interest.<p>Incidently, I happen to be an electrical engineer. At one point, I held a First Class Radiotelephone License issued by the FCC. I have been involved with electronics for over 45 years, either professionally or as a hobby. Over the years, I have accumulated a fair number of technical books, many of them dealing with radio. Some of these were from the 1920's and 1930's. I don't feel particularly ignorant of either the history or the practice of radio.<p>Offhand, I can't think of any major development in radio that is creditable to either Edison or Tesla. Edison came closest, with the observation of the Edison effect, but he never applied that to radio and the further development of the vacuum tube was done by other inventors such as Fleming and De Forest.<p>J. P. Morgan may have done Tesla a favor when he discontinued his support of Tesla's wireless power transmisssion project. Spark transmitters were notorious for creating interference, and Tesla's installation may have been capable of jamming a fair fraction of the radio communication in the Northeastern United States. Locally, it might have made the telephone system in New York inoperable. Another victim could have been the telegraph and signalling systems used by the railroads. I wonder if Morgan was thinking of the potential lawsuits as well as the economics when he pulled the plug.<p>[ December 23, 2004: Message edited by: stephen ]</p>

[Bernius1]

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......

[jwax]

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

[rshayes]

no_vice-<p>Yes the ground really conducts, sort of. The resistance of the ground depends on the type of soil and its moisture content. The variation is probably ohms to hundreds of ohms.<p>The capacitance of the human body is probably about 1000 picofarads. I seem to remember values in this range specified for electrostatic discharge testing. It certainly isn't farads.<p>The resistance of human skin is moderate. Actually, most of the resistance is in the interface between the skin and whatever you are contacting. Gripping the probes on a VOM wouuld show about 5 to 10 kilohms resistance. Add a little moisture and this can drop very low. Once contact is made, the flesh under the skin is very conductive, more in the range of ohms.<p>If the neutral wire is ungrounded the potential is unpredictable. If other houses are on the same circuit, the neutral will still be grounded, but thier ground potential may be slightly different from yours. If the circuit is indeed floating, then the capacitive coupling within the distribution transformer may allow some AC current to flow. I don't know about large transformers, but small transformers can have capacitances between windings of about 1000 picofarad. This may not seem much, but it can pass noticable currents even at 60 Hz.<p>Twisted pair power lines would both radiate less interference and pick up less interference. The field cancellation works in both directions.<p>MrAl-<p>The peak voltage is the consideration when you are choosing insulation. Arcs form very quickly once the breakdown voltage is exceeded. I think you will find that insulators that are rated for both AC and DC have a DC rating that is coincidently about 40 percent higher that the RMS AC rating.<p>Dale Y-<p>In your calculations did you include the return path? The DC and single phase AC lines will be carrying 3875 amperes south in one line and 3875 amperes north in the other line. I'm not sure how the currents will distribute between the wires in a 3 phase system, but there has to be a return current somewhere. Otherwise, the current would return through the ground, and I'm not very comfortable with the thought of 10,000 amperes flowing 800 miles through the ground.

[perfectbite]

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]

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]

<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]

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