Inventions
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Author | Topic: Inventions |
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Shaper
Member # 73
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written Monday, June 19 2006 06:32
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Thuryl, that would be "Gooble gobble", not "Gobble gobble", according to a quick Google search. Therefore, zomg turkey ![]() -------------------- My Myspace, with some of my audial and visual art The Lyceum - The Headquarters of the Blades designing community The Louvre - The Blades of Avernum graphics database Alexandria - The Blades of Exile Scenario database BoE Webring - Self explanatory Polaris - Free porn here Odd Todd - Fun for the unemployed (and everyone else too) They Might Be Giants - Four websites for one of the greatest bands in existance -------------------- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Posts: 2957 | Registered: Thursday, October 4 2001 07:00 |
Agent
Member # 5814
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written Monday, June 19 2006 07:28
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quote:At least it'd be something new. "Leave your sanity at the door" got old a long time ago. quote:And how will you make it only shoot at squirells? -------------------- quote: Posts: 1115 | Registered: Sunday, May 15 2005 07:00 |
Off With Their Heads
Member # 4045
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written Monday, June 19 2006 07:31
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quote:Something just occurred to me: What you're saying is limited to simple Newtonian equations, right? I mean, one of the problems with magnetism is that permanent magnets don't have simple laws underlying them, because permanent magnetism is a quantum effect. Because, clearly, a permanent magnet sitting on a table near a small piece of metal can do some work, attracting the metal towards it. [ Monday, June 19, 2006 07:33: Message edited by: Kelandon ] -------------------- Arancaytar: Every time you ask people to compare TM and Kel, you endanger the poor, fluffy kittens. Smoo: Get ready to face the walls! Ephesos: In conclusion, yarr. Kelandon's Pink and Pretty Page!!: the authorized location for all things by me The Archive of all released BoE scenarios ever Posts: 7968 | Registered: Saturday, February 28 2004 08:00 |
Electric Sheep One
Member # 3431
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written Monday, June 19 2006 09:26
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Yeah, he should only have been talking about magnetic fields doing no work on spinless electric charges. A magnetic field that varies in space can indeed do work on a magnetic moment. Lots of kinds of particles have intrinsic magnetic moments because of their spin, which is in some senses a quantum property. And ferromagnetism is indeed a phenomenon of spins. Even classically, though, *i's remark deserves some comment, because you can make a classical magnetic moment out of moving charges, for instance by running current around a loop. I have a primitive electric motor which consists of a wire loop free to spin in a frame, with a current driven through the wire by a battery. Nothing happens except for the wire getting warm, until you put a small fridge magnet under the loop. Then it spins like the dickens. It could power a small toy car. (For the experts: the reason it keeps spinning around, instead of just swinging back and forth because the torque reverses once the loop flips 180 degrees, is that the wire is insulated on one side only, so that the current is blocked and the torque ceases when it would otherwise be reversed. Half of every revolution by the loop is unpowered, but when it does get torque, it always gets it in the same direction.) The fact that you do need the battery indicates that the magnet is not driving the loop around all by itself. The magnet does not wear out or run down, though the battery does. And ferromagnetism is only involved here in the fridge magnet that creates the magnetic field; the motion of the loop is just about moving charges, not spin. So since *i is quite right about magnetic fields doing no work on moving charges, the magnet does no work in making the loop spin. Yet the magnet does make the loop spin, in the sense that the loop spins if and only if the magnet is present; and the spinning loop can certainly do work itself, so work is being done on it by something. I leave the resolution of this paradox as an exercise for the reader. -------------------- We're not doing cool. We're doing pretty. Posts: 3335 | Registered: Thursday, September 4 2003 07:00 |
Law Bringer
Member # 335
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written Monday, June 19 2006 14:53
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I invented a resolution to the paradox. —Alorael, who won't reveal it until he has it firmly copyrighted, patented, trademarked, and copy protected. Posts: 14579 | Registered: Saturday, December 1 2001 08:00 |
Infiltrator
Member # 3441
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written Monday, June 19 2006 17:51
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quote:I don't know that we have the capability to distinguish different animals from one another. It is currently programmed to only shoot blue objects. But that's because the really good programmers aren't working on it. This robotics club does some serious stuff, such as the DARPA Grand Challenge, as well as national UAV, unmanned sub, and unmanned ground vehicle competions, where they have to recognize complex obstacles and avoid them. Our current simplistic setup works by taking the data from the camera and turning it into a 2D array of RGB values, the centroid of the blue values is found and the turret is moved until the centroid is in the center of the camera, which is aligned with the barrel of the gun. This is pretty much the most basic way imaginable to visually track something, and adjustments need to be made for situations where there are multiple objects in view, which confuses the above mentioned algorithm. I can't tell you much more than that, since I've been working on the mechanical side of the project. -------------------- "As our circle of knowledge expands, so does the circumference of darkness surrounding it." --Albert Einstein -------------------- Posts: 536 | Registered: Sunday, September 7 2003 07:00 |
The Establishment
Member # 6
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written Monday, June 19 2006 18:18
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quote:No, what I said applies to relativity and quantum mechanics. While it is true, that ferromagnetism is a quantum property, the fundamental idea that magnetic forces do no work to a free charge is always true. Wikipedia sums up the argument best in Griffiths: quote:While it is true things like ferromagnetism have only a quantum mechanics description, Maxwell's equations and the Lorentz Force law are still valid. -------------------- Your flower power is no match for my glower power! Posts: 3726 | Registered: Tuesday, September 18 2001 07:00 |
Law Bringer
Member # 6785
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written Monday, June 19 2006 18:22
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quote:Define squirrels as the targets, then all the targets that are hit squirrels by definition. Just because everyone else thinks that you are targetting everything is immaterial. Posts: 4643 | Registered: Friday, February 10 2006 08:00 |
Guardian
Member # 6670
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written Monday, June 19 2006 18:52
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By WKS: quote:We have a similar set-up at my uni. It's an Segway that tracks and kicks soccer balls. You quickly discover that it's a bad idea to walk into that particular lab with a brightly coloured shirt on. The bot attempts to close the distance between itself and the perceived ball in the distance as quickly as possible. -------------------- I prefer my homicidal robots quasi-sentient. At least then you can reason with them. Posts: 1509 | Registered: Tuesday, January 10 2006 08:00 |
Electric Sheep One
Member # 3431
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written Tuesday, June 20 2006 04:42
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quote:But the Lorentz force isn't the only force. There is also the magnetic moment term in the Hamiltonian, \vec{\mu}\cdot\vec{B}. Check out the non-relativistic limit of the Dirac or vector Klein-Gordon equations to see that this term is really there. If this term is not constant, it exerts a force. Classical spinless moving charges can produce magnetic moments, leading to the paradox posed above, in which magnetic fields do no work but do enable work to be done. But relativity and quantum field theory together give particles intrinsic magnetic moments, and so real particles do experience non-Lorentz forces from magnetic fields, which can do work. -------------------- We're not doing cool. We're doing pretty. Posts: 3335 | Registered: Thursday, September 4 2003 07:00 |
Law Bringer
Member # 2984
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written Tuesday, June 20 2006 06:11
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quote:Now the only remaining problem is to breed blue squirrels... -------------------- Encyclopaedia Ermariana • Forum Archives • Forum Statistics • RSS [Topic / Forum] My Blog • Polaris • I eat novels for breakfast. Polaris is dead, long live Polaris. Look on my works, ye mighty, and despair. Posts: 8752 | Registered: Wednesday, May 14 2003 07:00 |
Off With Their Heads
Member # 4045
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written Tuesday, June 20 2006 07:06
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quote:If the magnetic field isn't doing any work when a bar magnet picks up a ball bearing, then which force is doing that work? The electric force? And how does it do it? I know that friction is proportional to the normal force, so I get the analogy, but I thought that the only relationship between electric fields and magnetic fields (classically) was that a change in one creates the other, and I don't think that a bar magnet creates a changing magnetic field, so I'm a bit befuddled. -------------------- Arancaytar: Every time you ask people to compare TM and Kel, you endanger the poor, fluffy kittens. Smoo: Get ready to face the walls! Ephesos: In conclusion, yarr. Kelandon's Pink and Pretty Page!!: the authorized location for all things by me The Archive of all released BoE scenarios ever Posts: 7968 | Registered: Saturday, February 28 2004 08:00 |
Electric Sheep One
Member # 3431
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written Tuesday, June 20 2006 11:16
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quote:Hmmm, this seems to be a limitation of Wikipedia. The non-constant field of a bar magnet pulls on nuclear and electronic spins in a ferromagnetic material, and this does do work. I don't have Griffiths at hand to judge whether the error is in Griffiths or by the Wikipedia writer. The resolution to my paradox in the absence of spin, I have just realized, is startlingly simple. If we have a system of more than one spinless charged particles, the total force on the system's center of mass, from all the Lorentz forces on the individual particles, will in general do work on the center of mass. (It is easy to work out what 'in general' means for the case of two particles in a constant magnetic field; it really does mean, 'except in a few very special cases'.) For spinless particles the magnetic field still does no work on the system as a whole. This just means that it does negative work on the relative co-ordinates among the particles. This may sound strange, but there is absolutely nothing odd about it, really. Suppose two oppositely charged particles of equal mass begin moving towards each other at equal speed. The center of mass has zero kinetic energy (it is not moving). In a constant magnetic field the two particles move in circles at the same rate (and at constant velocity) but in opposite orbital directions. So after 1/4 of a circle each, they are moving in the same direction. The center of mass now has positive kinetic energy, even though the total kinetic energy has not changed. The relative co-ordinate -- the separation between the two particles -- is at this moment not changing at all, so it has zero kinetic energy. It began with positive kinetic energy; it has received negative work, from the magnetic field. So can a magnetic field do work on a composite object? To remove the issue of spin, which does allow magnetic fields to do work quite unambiguously, we can rephrase the question as, Can the Lorentz force do work on a composite object? And now the answer depends entirely on what you mean by the object. If you mean its center of mass, then the answer is yes, in spite of Griffiths and anybody else. If you mean the total work done on all of the object's components, then the answer is no. Since the answer thus depends on terminology, you can have it either way you want, if you really want. I'd submit, though, that in cases where all of an object's relative co-ordinates are held tightly together by non-magnetic forces, but the center of mass is comparatively very free, then the practical question, and the one that most people would naturally want to ask, is about the work done on the center of mass. Internal forces do not affect the center of mass at all, so the magnetic force is the only explanation available for acceleration or deceleration of the center of mass. [ Tuesday, June 20, 2006 12:31: Message edited by: Student of Trinity ] -------------------- We're not doing cool. We're doing pretty. Posts: 3335 | Registered: Thursday, September 4 2003 07:00 |
Lifecrafter
Member # 34
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written Tuesday, June 20 2006 19:00
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I made a flute that played itself. Needless to say, it totally blew. [ Tuesday, June 20, 2006 19:01: Message edited by: Robinator, #034 ] -------------------- Frisbeetarianism is the belief that when you die, your soul goes up on the roof and gets stuck. 'Spiderweb Software' anagrammmed: 'Word-bereft A**wipe' Posts: 702 | Registered: Wednesday, October 3 2001 07:00 |
The Establishment
Member # 6
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written Tuesday, June 20 2006 20:31
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quote:You are correct and Griffiths is as well. To clarify my last post, work cannot be done on a free charge, but can on a magnetic moment. There is the key distinction. The force felt by the moment is: F = mu*dB/dx F = force mu = magnetic moment B = magnetic field The work done rotates the magnetic moment along the magnetic field. The complication from quantum mechanics lies in the intrinsic magnetic moments in particles. The classical formulation is correct if one assumes a dipole moment. [ Tuesday, June 20, 2006 20:52: Message edited by: *i ] -------------------- Your flower power is no match for my glower power! Posts: 3726 | Registered: Tuesday, September 18 2001 07:00 |
Electric Sheep One
Member # 3431
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written Tuesday, June 20 2006 22:30
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The magnetic moment force can also just speed particles up or slow them down, like gravity or electrostatic force. If the direction of B is constant, then the projection of the intrinsic magnetic moment along the magnetic field direction will not change either. So the interaction energy \mu\cdot B is then in this case simply a potential acting on the particle's position. Magnetic traps for neutral atoms work this way. -------------------- We're not doing cool. We're doing pretty. Posts: 3335 | Registered: Thursday, September 4 2003 07:00 |
Master
Member # 5977
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written Wednesday, June 21 2006 01:10
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quote:Is it in the same family of the self-playing piano, of which I forgot its name? -------------------- Play and rate my scenarios: Where the rivers meet View my upcoming scenario: The Nephil Search: Escape. Give us your drek! Posts: 3029 | Registered: Saturday, June 18 2005 07:00 |
Agent
Member # 6581
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written Wednesday, June 21 2006 02:24
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Inventions? I would make an implant: a computer IN your arm that recarge itself with your physical energy. -------------------- Download Geneforge 4: Rebellion You have 6 posts. Nobody cares what you think. - Thuryl Wikipedia may be your friend, but UBB is not. - Dikiyoba Posts: 1310 | Registered: Tuesday, December 20 2005 08:00 |
Law Bringer
Member # 4153
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written Wednesday, June 21 2006 04:42
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quote:Yay! Let's make modern technology even more of a parasite with respect to our lives! -------------------- Gamble with Gaea, and she eats your dice. I hate undead. I really, really, really, really hate undead. With a passion. Posts: 4130 | Registered: Friday, March 26 2004 08:00 |
Lifecrafter
Member # 6403
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written Wednesday, June 21 2006 07:23
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Why not? If people want it, let them go ahead and get it. Myself, I've always wanted an mp3 player embedded into my body so I would be able to listen to music at all times. -------------------- ??? ?????? ???? ????? Posts: 883 | Registered: Wednesday, October 19 2005 07:00 |
Lifecrafter
Member # 34
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written Wednesday, June 21 2006 19:04
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I invented the dictionary. My parents said they were so proud they couldn't put it into words. [ Wednesday, June 21, 2006 19:05: Message edited by: Robinator, #034 ] -------------------- Frisbeetarianism is the belief that when you die, your soul goes up on the roof and gets stuck. 'Spiderweb Software' anagrammmed: 'Word-bereft A**wipe' Posts: 702 | Registered: Wednesday, October 3 2001 07:00 |