dp wrote:> When the electrons move inside a conductor (metal), this effect > is seen as a mechanical force applied to the _conductor_. It takes > electric rather than magnetic field to move electrons inside the > conductor. This is how electric motors work. You _cannot_ affect > the path of the electrons inside the conductor by a static magnetic > field, just as you cannot force them to exit the conductor.If true, then why do superconductors have a critical magnetic field level. Moving electrons are influenced by magentic fields, the key question, is how much ? -jg
BGA central ground matrix
Started by ●February 1, 2006
Reply by ●February 3, 20062006-02-03
Reply by ●February 3, 20062006-02-03
Austin Lesea wrote:> As I already said, I will post some results (when I find them).I've given seminar talks for the last 20 years pressing designers to constantly reevalutate the underlying assumptions in a design, as they frequently change, and with small invalidations in the foundation, the whole design can, and does, fail. Actually to document them, and well. As a consultant tackling failed projects, one reoccuring theme when I started probing the design/architecture was asking questions about the assumptions and getting the "everybody knows ..." answer. The "we have always done it that way, and it works ..." answer. Well, why is it now broke? This is another case of "everybody knows", that will be fun to add to my on going talk, "It's not what you know that will hurt you, it's what you think you know" as a case study :)
Reply by ●February 3, 20062006-02-03
Austin Lesea wrote:> Paul, > > The latter (b). > > They do carry current, but it is falling off as 1/r or 1/r^2 (I just > can't remember which). > > The BART rails had 2/3 nearest the power rail, and 1/3 in the rail > furthest. Which makes me think it was 1/r, not 1/r^2. > > Also, BART has shorting links every X meters that ties the two rails > together (now) to lessen the return resistance (improve efficiency).Hmmm....> I think I was told that the inner 2X2 balls had 1/8 to 1/16 the > current...but it may have been more (or less).Hmmmm....> As I already said, I will post some results (when I find them).Please do, we can agree there is an effect, my antennae just question how much of an effect at DC ?. You still have to satisfy ohms law, so any push effects that favour flow, have to model somehow as mV(uV) generators.... To skew Ball DC currents 7/8 or 15/16, frankly sounds implausible, and maybe the models there forgot to include resistance balancing effects ? [ ie do not believe everything you are 'told' ] -jg
Reply by ●February 3, 20062006-02-03
<fpga_toys@yahoo.com> wrote in message news:1138992533.556317.212590@g49g2000cwa.googlegroups.com...> > As a consultant tackling failed projects, one reoccuring theme when > I started probing the design/architecture was asking questions about > the assumptions and getting the "everybody knows ..." answer. The > "we have always done it that way, and it works ..." answer. Well, why > is it now broke? >That's the monkey story. http://www.wowzone.com/5monkeys.htm Monkeys are funny. :-) Cheers, Syms.
Reply by ●February 3, 20062006-02-03
Jim, It has to do with current creating a magnetic field, and how the magnetic fields interact. Imagine I have a rectangular loop (tall and skinny), divided down the middle by a sheet of glass. On either side of the glass I have a scale (made of plastic) to see how much the wire pulls away from the glass as the current increases in the loop. At some point, I add a third wire on one side of the glass in parallel. It is some distance away from the glass, more so that the first set of wires. What I claim is that the force of the third added wire will be less than that of the first wire, and the force of the first on the same side of the glass wire will be somewhat less, but will not be 1/2. In fact with the BART rail spacing, it would be 2/3 and 1/3. At DC. Guess what? Current creates a field, a field tells current how to flow. I think Faraday discovered this? This works by the way for superconducting wires, resistance has no part in this. R does not appear in the equations to show this is true. QED for this "Gendanken" Experiment... Austin Jim Granville wrote:> Austin Lesea wrote: > >> Paul, >> >> The latter (b). >> >> They do carry current, but it is falling off as 1/r or 1/r^2 (I just >> can't remember which). >> >> The BART rails had 2/3 nearest the power rail, and 1/3 in the rail >> furthest. Which makes me think it was 1/r, not 1/r^2. >> >> Also, BART has shorting links every X meters that ties the two rails >> together (now) to lessen the return resistance (improve efficiency). > > > Hmmm.... > >> I think I was told that the inner 2X2 balls had 1/8 to 1/16 the >> current...but it may have been more (or less). > > > Hmmmm.... > >> As I already said, I will post some results (when I find them). > > > Please do, we can agree there is an effect, my antennae just question > how much of an effect at DC ?. > > You still have to satisfy ohms law, so any push effects that favour > flow, have to model somehow as mV(uV) generators.... > To skew Ball DC currents 7/8 or 15/16, frankly sounds implausible, and > maybe the models there forgot to include resistance balancing effects ? > [ ie do not believe everything you are 'told' ] > > -jg > > > >
Reply by ●February 4, 20062006-02-04
Austin Lesea schrieb:> What I claim is that the force of the third added wire will be less than > that of the first wire, and the force of the first on the same side of > the glass wire will be somewhat less, but will not be 1/2. In fact with > the BART rail spacing, it would be 2/3 and 1/3. > > At DC. > > Guess what? Current creates a field, a field tells current how to flow. > > I think Faraday discovered this?;-) This is really funny. A very basic effect of physics is "forgotten" by the highly trained specialists. Maybe I can jump in and help to enlight the non-belivers. The effect in question is called Lorentz-Force (Lorentz-Kraft in german). Its the effect that makes every electrical engine spin. Just have a look at those small toy motors, they use a permanent magnet to greate a static magnetic field and a DC current inside the rotator loop. OK, the current gets reversed by the commutator every fraction of a revolution, but this is not the point. Another example is the good old CRT TV set. A (quasi) magnetic field is used to deflect a electron beam (moving charge carriers).> This works by the way for superconducting wires, resistance has no part > in this. R does not appear in the equations to show this is true. > > QED for this "Gendanken" Experiment..."Gedanken"Experiment. Just a small typo. (yeahh, germans are known to be real pedantic ;-) Regards Falk P.S. To be onest I never thought of the magnetics stuff before when looking at the GND/VCC balls on a package. Interesting!
Reply by ●February 4, 20062006-02-04
Falk, Thank you. I only had three years of high school German, so forgive my spelling. Just think how surprised those Westinghouse Engineers were when they had 10,000 trains....and 6 empty train blocks light up on the 10 meter by 3 meter map display! Austin Falk Brunner wrote:> Austin Lesea schrieb: > >> What I claim is that the force of the third added wire will be less >> than that of the first wire, and the force of the first on the same >> side of the glass wire will be somewhat less, but will not be 1/2. In >> fact with the BART rail spacing, it would be 2/3 and 1/3. >> >> At DC. >> >> Guess what? Current creates a field, a field tells current how to flow. >> >> I think Faraday discovered this? > > > ;-) This is really funny. A very basic effect of physics is "forgotten" > by the highly trained specialists. > > Maybe I can jump in and help to enlight the non-belivers. The effect in > question is called Lorentz-Force (Lorentz-Kraft in german). Its the > effect that makes every electrical engine spin. Just have a look at > those small toy motors, they use a permanent magnet to greate a static > magnetic field and a DC current inside the rotator loop. OK, the current > gets reversed by the commutator every fraction of a revolution, but this > is not the point. Another example is the good old CRT TV set. A (quasi) > magnetic field is used to deflect a electron beam (moving charge carriers). > >> This works by the way for superconducting wires, resistance has no >> part in this. R does not appear in the equations to show this is true. >> >> QED for this "Gendanken" Experiment... > > > "Gedanken"Experiment. Just a small typo. (yeahh, germans are known to be > real pedantic ;-) > > Regards > Falk > > P.S. To be onest I never thought of the magnetics stuff before when > looking at the GND/VCC balls on a package. Interesting!
Reply by ●February 4, 20062006-02-04
austin schrieb:> Just think how surprised those Westinghouse Engineers were when they had > 10,000 trains....and 6 empty train blocks light up on the 10 meter by 3 > meter map display!Hmm, but why didn't they have a small prototype for testing? Or did they think this is sooo trivial no need for testing? Regards Falk
Reply by ●February 4, 20062006-02-04
Falk, I have no idea. But they (Westinghouse) had never done a modern urban transit system before, and had been given the contract. Politics, pork, etc. There were many at the time who said that this was yet another example of incompetence, and that the contract should have been given to the experts in electric traction urban transit...who were Germans (at that time). All in all, the system was well engineered, and was very modern (when introduced). IBM did the payment system, which was so easy to clone that students bragged about how they could make copies of their $20 cards with nothing but a flat iron. (Do not know if this was true or not). Presumably that got fixed ... Austin Falk Brunner wrote:> austin schrieb: > >> Just think how surprised those Westinghouse Engineers were when they >> had 10,000 trains....and 6 empty train blocks light up on the 10 meter >> by 3 meter map display! > > > Hmm, but why didn't they have a small prototype for testing? Or did they > think this is sooo trivial no need for testing? > > Regards > Falk
Reply by ●February 4, 20062006-02-04
>Anyone who can point to a clear and simple explanation, please do.>When I first mentioned this to our packaging group, the lead engineer >said "oh yes, I see this in the EM simulations..."I think the key idea is that the return current is flowing close to the forward current. Or rather closer to parts of the conductor than it is to the rest. What's the current distribution in the center conductor of a coax carrying DC? Where are the balls carrying the "return" current relative to the central clump of ground balls??>So, I know I am not imagining it!Simulations never get the wrong answer? [I used to be reasonably good at this stuff, but that was a long long time ago. This feels like a good question for PHD orals.] -- The suespammers.org mail server is located in California. So are all my other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited commercial e-mail to my suespammers.org address or any of my other addresses. These are my opinions, not necessarily my employer's. I hate spam.
