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Subject:
Kinetic versus Potential Energy and the Conundrum of Magnetism
Category: Miscellaneous Asked by: punkycry-ga List Price: $2.00 |
Posted:
06 Jan 2006 05:09 PST
Expires: 05 Feb 2006 05:09 PST Question ID: 429890 |
If one considers the good old 'fridge' magnet as an example, one observes that it does, and can, hold a considerable mass before being overcome by gravity and falling to the floor. Yet it does this without any apparent consumption of energy. We can take that same magnet, pass it perpendicular to a piece of copper wire and electrons flow in the copper conductor producing electricity, yet that reaction required that motion be invoked and we subsequently would call the result as kinetic energy. In the fridge magnet, the magnetic field of the magnet itself could be considered potential energy yet there is the apparent lack of any motion, or more specifically, 'work done' that would require the expenditure of energy. How is it then that the magnetic can oppose the force of gravity - it would seem indefinitely - without 'consuming' any energy? In a similar vein, a magnet will induce a magnetic field into a ferrous object (such as the good old magnetic screwdriver) giving it the same property: being able to pickup errant screws, holding onto them and again preventing the mass of the screw(s) to counteract the force of gravity without any apparent energy input while leaving the strength (gauss) of the original magnet intact. As far as we (I) know, no fridge magnet has ever 'succumbed' to gravitational forces and relinquished its magnetic properties - at least not in human observational time frames! So, if this is not 'Kinetic' energy that is keeping this fridge magnet (and its associated attached mass) from falling to the floor because of gravity - then what is it? If one considers the tenets of basic physics: energy is neither created nor destroyed, and "FORCE=MASS multiplied by ACCELERATION", then how can this magnet continue to defy the force of gravity without doing any apparent "WORK"? Many have tried to create the Perpetual Motion 'Machine' but to no avail - it simply exists as a fictional urban myth. The fridge magnetic would appear to be such although it perhaps does not qualify since it is not moving per se. Or is it? It, and the rest of earth is in fact moving in space time and many have concluded that the universe is actually accelerating. Einstein in all his wisdom was frustrated by not being able to wrap his head around gravity and it was one enigma he took with him to his grave. Today, the search for the gravity answer is the 'holy grail' of theoretical physics researchers. Could it be that the answer to the "fridge magnet" analogy question is still elusive, or have I missed something elementary here? A tank of gasoline is clearly potential energy and can do no work until ignited in an engine whereby once the process of motion is invoked by the spark of the internal combustion engine which proceeds to drive the apparatus (car) to a destination - UNTIL that is, the gasoline is consumed - at which point it wilol obviously cease to move until refuelled at the next gas station. The fridge magnet on the other hand - appearing to be doing 'work' because it relentlessly 'holds' itself and its appendages in opposition to the gravitational force that conspires to bring it crashing to the ground - does NOT need fuel. Where then does it continue (like the elusive perpetual motion machine) to derive its mysterious 'power'? Why do I 'torture' myself with this and why can't I simply accept (and I do appreciate) my fridge magnets as the 'magical' entities that they appear to be? I suspect though that there is an answer and that its not merely a magician's 'trick'! The question (questions!) provoked by the fridge magnet paradigm in my mind go well beyond mere curiosity - if we can harness what might be an unencumbered energy source that is at once "eco-friendly", ubiquitously available (essentially free?) and that could be practically implemented - it would change forever our relstionship with Mother Nature (hopefully in a good way!) and break our dependence on non-renewable energy techologies which are literally destroying our planet. And in the same vein, parting ways with the - at times - despicable political implications of reliance on the destabilising influence of the conventional energy sector controlled substantially by despotic regimes that are more than willing to take our money, and our good will, whilst knifing us in the back because of their historical hatred of us, and their religious fundamentalism. So - thats the longer question. Blame it on the fridge magnet. Your comments wilol be appreciated. |
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There is no answer at this time. |
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Subject:
Re: Kinetic versus Potential Energy and the Conundrum of Magnetism
From: curious987-ga on 06 Jan 2006 20:25 PST |
OK. according to this site: http://my.execpc.com/~rhoadley/magfree.htm there is no way to get "free" energy from magnets, and magnets are not perpetual motion devices. I believe that non-permanent magnets are obviously magnetized and can be de-magnetized. It's like if you have a generator that powers a motor that powers the generator. With permanent magnets, it's a bit trickier to explain but this technical (in my opinion) paper does a good job of explaining why permanent magents are not "free" sources of energy. Again, I'm not a physicist, so please correct me if I'm wrong. I hope this helped! |
Subject:
Re: Kinetic versus Potential Energy and the Conundrum of Magnetism
From: socraticinstlouis-ga on 13 Jan 2006 22:21 PST |
I think the answer to your question is right here, where you write: "The fridge magnet on the other hand - appearing to be doing 'work' because it relentlessly 'holds' itself and its appendages in opposition to the gravitational force that conspires to bring it crashing to the ground - does NOT need fuel." There isn't any work being done when "holding" a mass so that it doesn't accelerate in a gravitational field. There's no difference, in a thermodynamic sense, between a postcard being pressed against the outside of a refrigerator door by a magnet (assuming the 'pressing' force is enough to cause friction from allowing the whole thing from sliding down the door), and a postcard resting on a table. There is zero energy-conversion happening in either case. The mechanism of the *force* production is different, but there are many ways of producing force which don't involve ongoing energy conversion: magnetism is one, the (slight) compression of the table leg supporting the top of the table and thus the postcard is another, gravity is one, electrostatic forces (static electricity), differential aerodynamic pressure as from a static vacuum chamber, the list goes on and on. There might be some energy conversion during the initial generation of the force, but there is no ongoing source or sink of energy involved in many of these situations. Magnetism is not energy. It's simply a 'mechanism'. |
Subject:
Re: Kinetic versus Potential Energy and the Conundrum of Magnetism
From: firewolf-ga on 01 Feb 2006 19:24 PST |
As a HS Science teacher I have a few comments. 1. No work is being done. Work = Force x distance. That said, since the magnet is NOT moving (in relation to the force of gravity of earth, which is where physics is based), it would not matter what the force or size of the magnet was. 2. Power = work done over time. So again, since there is no work being done, there is NO Power. 3. Kinetic Energy is energy in MOTION, so again, the magnet is stationary, therefore all energy is STORED, or Gravitational Potential energy. Now, if the magnet were to start sliding down the surface of 'fridge, the energy would be transfered from potential to kinetic. In this case, there would then be work done (if minor), and power. Go to Physicsclassroom for more information. |
Subject:
Re: Kinetic versus Potential Energy and the Conundrum of Magnetism
From: browha-ga on 02 Aug 2006 02:46 PDT |
Firewolf is exactly right. F=MA, but the F there is resultant force. Since there is no motion, there is no resultant force. Gravity and the magnetic attraction balance each other out perfectly. It is all held as Gravitational Potential energy, in the mass, and as soon as the resultant force is the weight of the object, it will accelerate towards the ground at a value of g, converting GPE into KE. Perpetual motion machines arent, as such, an aspect of science fiction, it is quite real. Just impossible (practically) to obtain. Very simply, an object similiar to the London Eye could easily be a perpetual motion machine. The only things I can think of off hand that prevents it from doing so is... a) Wind resistance b) Internal friction Transformers are very highly efficient, I was taught at school they approach 100% efficient (not quite exactly that, some flux is still lost and some heating of lubricants still occurs). |
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