Naked Science Forum
Non Life Sciences => Technology => Topic started by: clueless on 08/10/2012 16:27:56
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I have a question about magnets. You are stuck in a room. Its ceiling, which is about 5 m high, is an extremely strong type of magnet, which can be activated by pressing the wall button. You are holding an iron ring in your hand the size of an aureole. Is it at all possible that if you’re holding the ring when you press the button, the magnet will lift you all the way to the ceiling? In a film, as Bond is fighting with Jaws, he activates and positions magnet to lift Jaws by his metal teeth. But in the film, the magnet was real close to Jaws' teeth. Could a super magnet lift a person from a higher height, like 2 m? How about 5 m, or more? Is that at all possible? Could that be possible in the future as science progresses? Thanks.
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If they are polishing the floor ... http://www.thenakedscientists.com/forum/index.php?topic=20556.msg229916#msg229916
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The question is a little complicated to answer. In the way the questioner intends, it could not be done with any form of simple electromagnet in the ceiling. The magnetic field would fall off quickly with distance, so the auriole (I assume this means a halo sized ring of magnetic material like iron) would be attracted much more powerfully if it was close to the ceiling rather than near the floor. Rather like the James Bond scene with Jaws, the force can be very strong if very close but would not be very strong some distance away.
The strong field in a MRI scanner is because the whole tube the patient lies in is part of the magnet. The patient experiences a roughly constant magnetic field in the direction of their body: head to toe or vice versa. To duplicate this in a room would require coils of superconducting wire around the room and probably extending above and below the room for some distance. The horizontal dimensions would have to be kept small if the field was to be high so, effectively, it would be like being in a large MRI scanner tipped up on its head. By controlling the field with some feedback based on the position of the halo and perhaps controlling the smaller fields, that would try to pull the halo off its central axis, via some smaller oscillating field electromagnets working horizontally, it should be possible to lift a person and hold the halo at a controlled position.
This would be a very expensive piece of kit though. You would have to question "why?"
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This is helpful. 8D
This would be a very expensive piece of kit though. You would have to question "why?"
I'm working on a riddle. I'm a puzzler on the Wu forums. ::)
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If I've understood the scenario correctly, and the size of the piece of iron, then the magnetic field would have to be so large and so powerful that you could float the person using the diamagnetism of their body's water without the iron being there at all.
Iron saturates at a couple of Tesla, which with any normal applied magnetic field would give you a few kilograms of lifting, but the lift goes as a product of the field generated by the iron and the applied field, so you would need maybe a 20 Tesla applied field over the room; which is a massive, massive field over such a large volume, enough to give the diamagnetic levitation effect without the ring.
To put this in perspective, normal MRI machines are about 3-5 tesla.
Or maybe I've misunderstood how big the ring is. What is its size in centimetres?
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Or maybe I've misunderstood how big the ring is. What is its size in centimetres?
I guess there are different sizes of halos, but I was thinking that this iron ring is about 20 cm in diameter.
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If I've understood the scenario correctly, and the size of the piece of iron, then the magnetic field would have to be so large and so powerful that you could float the person using the diamagnetism of their body's water without the iron being there at all.
Iron saturates at a couple of Tesla, which with any normal applied magnetic field would give you a few kilograms of lifting, but the lift goes as a product of the field generated by the iron and the applied field, so you would need maybe a 20 Tesla applied field over the room; which is a massive, massive field over such a large volume, enough to give the diamagnetic levitation effect without the ring.
To put this in perspective, normal MRI machines are about 3-5 tesla.
Or maybe I've misunderstood how big the ring is. What is its size in centimetres?
I guess you'd want to make sure you took out any jewellery first!
Would it make a difference to the strength required if the metal ring was also electro-magnetised (ie. had a power source to increase it's magnetism)?
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Or maybe I've misunderstood how big the ring is. What is its size in centimetres?
I guess there are different sizes of halos, but I was thinking that this iron ring is about 20 cm in diameter.
That would probably bring it within the range of what MRI magnets can lift a person up with.
The other thing I will note is that MRI magnets aren't off and on-able. They take quite a while to magnetise, but once they're magnetised they're stable for months. So you'd have to move the magnet so as to pick someone up with it.
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Would it make a difference to the strength required if the metal ring was also electro-magnetised (ie. had a power source to increase it's magnetism)?
Probably not very much; it would take a lot of power to make a big difference.
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The kind of electro-magnetic locks they use to secure electronically-activated doors in offices and commercial premises are often rated to about 220kg of force. They're not much bigger than a large box of matches. This is "holding force" though, and will be a small fraction of that even with just a few mm separation between the magnet and the plate.
You get both "fail safe" and "fail secure" versions - the latter must contain a permanent magnet which still holds the door shut in the event that power is lost.
A magnet which could support the weight of a person hanging from a modestly-sized iron hoop with a gap of a metre or so would be a very big and powerful magnet indeed. If you had a nice (e.g. optical) feedback system, you could make the person hover nicely at a controlled separation from the magnet, rather than just slam into the magnet (ouch).
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OK,so I get this really huge magnet. Presumably, it's an electromagnet. I put some bloke in a room under it and I get him to hold onto the iron ring.
I turn on the power.
The magnet attracts the ring and lifts the guy up.
He reaches the ceiling and the magnet continues to attract the bit of the ring that he's holding onto.
The ring flips and lies horizontally on the ceiling.
If it was strong enough to lift him at 1 metre then it's going to be a whole lot stronger at about 1 cm.
So it cuts through his fingers.
He falls down.
Doesn't look like a good way of lifting someone.
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It would not be to difficult to fit the ring with suitable handholds so that his fingers would be safe, on a more serious note I wonder what these 20+ Tesla fields are to do to ones internals.
The idea of having an optical feedback circuit to produce floating may run into problems due to the slow rate at which the field of superconducting magnets can be modulated.
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The lifting strength of a magnet is a function of both the magnet, and the object being lifted.
You'd likely be better off with a steel plate vs a ring.
As far as scrambling your internal organs. Would it be any worse than an MRI, assuming that you don't have any steel implants, steel bullets, rings, and etc? The field, of course, drops with distance. So, your head will be a foot below your hands (assuming you are holding on with the fingers). The rest of the body will be below that.
Frogs are supposed to be able to at least survive strong enough magnetic fields to levitate the diamagnetic field in the water in their bodies.
Presumably pushing (with diamagnetics?) is safer than pulling with the magnetic field if you are wishing to levitate.
As with James Bond and Jaws... not all Stainless Steels have the same magnetic strength. Thus, it may in fact need to be a much stronger magnet than otherwise calculated.
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If I've understood the scenario correctly, and the size of the piece of iron, then the magnetic field would have to be so large and so powerful that you could float the person using the diamagnetism of their body's water without the iron being there at all.
Iron saturates at a couple of Tesla, which with any normal applied magnetic field would give you a few kilograms of lifting, but the lift goes as a product of the field generated by the iron and the applied field, so you would need maybe a 20 Tesla applied field over the room; which is a massive, massive field over such a large volume, enough to give the diamagnetic levitation effect without the ring.
To put this in perspective, normal MRI machines are about 3-5 tesla.
Or maybe I've misunderstood how big the ring is. What is its size in centimetres?
So relieved that MRI machines are "only" 3-5 Tesla. I had visions of patients spinning at high "g" in a spin rinse! ;D