Sure. Potential energy is converted to kinetic energy. Or vice versa.
And you’re reversing cause and effect. Gravity is the force. It exerts itself as a fundamental of mass.
Again, I think I am following you. The piece of iron moves from a higher potential energy state to a lower one when it moves closer to the magnet.
Is it correct to say that potential energy is absolute - that is, it is relative to the rest of the universe as a whole?
Regards,
Shodan
ETA: That’s what I get for running off to do something else before I finish typing. Ignore the below and re-read what Moriah said.
It’s the same energy that allows atoms to cling together and become molecules, or dense matter. You don’t understand it because none of us do yet. We know this though, that the splitting of an atom creates orders of magnitude more energy than the processing of whole atoms (i.e. burning wood or coal). Within themselves they hold a huge potential energy which is very difficult to extract in a controlled fashion. The processes which produce conventional energy may move whole atoms about, or even move them in and out of moleculor configurations and groups, but they don’t utilize the internal attractive and repulsive energy of the atom itself.
So, is it using energy? Yes. Is it going to get used up eventually? Yes. One way to see this happen is to create a weak electromagnet with an iron nail and a AA battery. Just run the current through it for a few seconds and then stick it to the underside of a metal shelf. You have magnetized only a small portion of it’s make-up and the effect will wear off (= the energy will get used up) very quickly. Watch for a few minutes and you will see it fall.
Given that a rare earth magnet has the same sort of energy stored densely in every atom of it’s makeup, it will take longer than your lifetime to watch it use up the energy and eventually fall. It will even go through a process of magnetizing the shelf, and the magnetic energy will spread and dilute for . . . well I really have no idea how long. you definitely will not live long enough to see it fall.
But I have always found it fascinating that we haven’t found a way to harness magnetic energy. the fact that we sell magnets as children’s toys kinda scares me. I suspect that some day humans will look back and wonder at our cavlier attitude about them.
If you really want to be intrigued, read up on magnetic induction cooking elements.
So in this example, the strands are simply occupying the positions of lowest potential energy. If there were no magnetic field present, and only Earth’s gravitational field, they would accomplish the same thing by hanging straight down (i.e., straight toward the Earth’s center). Because we see that sort of thing all the time, it doesn’t seem like something strange or requiring any sort of explanation; it’s just the way things are. But when you add the magnetic field, the positions of lowest potential energy change, and when the strands fall into those positions, they look odd to us. It looks like the strands are somehow being held in positions of higher potential energy, which would require a constant input of energy that would thus get “used up”. But nothing is getting used up, any more than Earth’s gravity is getting used up by attracting the strands to it.
Did I get that right?
I’m not sure. There seems to be an active force at work here. If I grab one of the strands at the bottom and push it toward the others, all of them move. It seems like the other 3 strands are being moved by something.
Ok, this makes sense to me. Energy is being used up, but because of the nature of atoms there is a huge amount of this energy, and it will take a long time before it’s used up.
atomic forces are at work. the atom stays together and it has properties. when atoms are near one another they can affect one another. if you add up the forces presented by a huge number of atoms then you can see a result such as a magnetic field.
Not at all clear what you’re talking about here, but you seem to have several forces confused. Atoms “cling together and become molecules” through the electromagnetic force, which is quite well understood. “the splitting of an atom” unleashes the strong nuclear force, which has nothing to do with magnetism.
Actually, this has very little to do with the energy being ‘used up’, and more to do with the fact that the iron in the nail doesn’t hold onto the magnetic charge very well or long no matter what. A magnet which is holding onto something isn’t using up stored energy. The magnetic domains just don’t hold well in some materials.
This is nonsense. We ‘harness magnetic energy’ in every single permanent-magnet generator in existence.
try this as an experiment and report back.
The big bang. Everything was in the same place once. Then a bunch of energy split it up and spread it around. When a magnet (or electrical particle, or a piece of matter) attracts something, you’re getting back some of the energy the big bang used to separate those things in the first place.
To be absolutely clear: A magnet that’s just sitting there (or just hanging there, whatever) isn’t using up any energy. You don’t need to spend energy to exert a force. The magnet just hanging there is just like your chair just sitting there: Both are exerting a force, and neither needs any energy at all to do so.
Yes, you are thinking about it wrong.
I haven’t read the whole thread, so my apologies if someone has already said this. It was not said clearly in the first few replies.
A force is only doing work, and thereby expending energy, if it is actually moving things. Your configuration of magnets, once it is set up, is not moving, right? Therefore it is not expending any energy.
“Maintaining” a force, as such, does not take energy. The Earth, for instance, does not expend any energy to maintain its gravitational field. Like any other object with mass, the Earth just has a gravitational field. The same goes for magnets and their magnetic field.
A magnet does not have to expend energy in order to stay stuck to a piece of iron (or to stay in the position that another magnet has repelled it to), any more than one end of my pen has to expend energy in order to remain attached to the other end. You would have to expend energy either to break the pen apart, or to pull the magnet off the iron, but then, that involves moving things.
ETA: Ninjaed by Chronos :mad:
Yes, by your hand. That is where the energy is coming from (in this case) that causes all the things to move. The precise way they move is determined by the local configuration of magnetic (and gravitational) forces, but those forces are not putting any energy into the event. The energy is coming from your muscles and, ultimately, from food you ate.
Love the explanations so far. The energy came from chemical energy released to move your muscles to move the magnet. And not only does an object have to be moving for a force to be doing any work, work is only done if the force has component in the same direction as the displacement. Carrying a book at a constant velocity across a room horizontally for example requires no work because the force you are applying is upward.
But if the magnet is hanging from the underside of a storage cabinet, doesnt it need to expend energy to fight gravity? If the magnetic force wasnt there, it would just fall.
No.
Do you think the bottom part of the cabinet has to expend energy to “fight gravity” in order to keep from falling off from the top part of the cabinet? Do your fingers need to expend energy in order not to fall off your hands? What if it wasn’t a magnet, but it was glued to the bottom of the cabinet? Do you think it would need to expend energy to stay there then?
To repeat, energy only gets expended when things move (or, more strictly, when they suffer either acceleration or deceleration).
No, these are good questions. It’s hard to make sense of what you’re seeing, because most phenomena we observe at the “macro” level seem to be more simple. Nonetheless, it all fits together.
The energy or force that’s making your buckyballs hover in the air is electromagnetism. According to the model of “life, the universe, and everything”, electromagnetism is one of the four fundamental forces of the universe, the others being gravity, strong force, and weak force. The last two are weird things that we only observe at the subatomic level.
Electromagnetism and gravity, however, are obviously important. The amount of gravitational force a magnetic object exerts is millions of times less than the amount of EM force it puts out. In short, gravity is very weak compared to EM, which is why your magnets seem to float.
The EM force in the magnets is very nearly an intrinsic part of their matter. It won’t last “forever”, for absurdly large values of forever, but it will last many billions of years. A neodymium atom has an intrinsic magnetic state that attracts or repels other magnets. It’s as much a part of the atom as its electrons. It’s a “feature” of the atom itself, and nothing has to be applied to it for this force to appear.
magnetism is a consequence of the state of the electrons in that substance.
Compare gravity v. gravity.
When the moon is overhead, it’s exerting a gravitational pull on us. If the earth were to magically disappear, we (and by we, I mean our corpses) would ‘fall’ into the moon’s gravity well until we crash into it and rest on its surface.
So, with the earth present, both the earth and moon are in a gravitation tug of war over us. The earth’s size and its proximity means it wins… but the moon is still pulling on us.
Same with the magnet ‘stuck’ to the underside of a cabinet. The strength and proximity of the magnet and iron keep them together though the earth is pulling down on the magnet. So where is the energy of the magnet coming from to keep it up? The same answer to where is the energy that keeps us stuck to the earth and not flying off to the moon: Fundamental force.
By its nature, mass has gravitational pull. By its nature an electrical charge has magnetic pull (or repulsion). Always on. Although… maybe in a few eternities all fundamental forces will expand to a weak probability wave that encompasses the entire universe and some infinite dimensional god will come along and say, “Why is this universe just some weak static?”
I think you’re getting hung up on conservation of energy and supposing how a fundamental force being ‘always on’ is violating that principle. The energy in any closed system always counts the ‘always on’ fundamental forces already present. It’s changes in the closed system that must balance out to a zero sum to conserve energy.