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Author Topic: How much magnet does it take to kill?  (Read 5561 times)

Offline ScientificSorcerer

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How much magnet does it take to kill?
« on: 16/03/2014 04:12:26 »
A magnet is a powerful thing, But How strong of a magnet do you need to kill?  For example with a strong enough magnet can you mess up your brain, or can a strong enough magnet rip the iron out of your blood? How many Teslas do you need to kill someone?

My bet is you'll need at least 50 teslas but that's just a guess.


 

Offline RD

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Re: How much magnet does it take to kill?
« Reply #1 on: 16/03/2014 05:25:37 »
... But How strong of a magnet do you need to kill?  For example with a strong enough magnet can you mess up your brain

Transcranial magnetic stimulation can cause seizures, and seizures can be fatal.

Quote from: wikipedia.org/Transcranial_magnetic_stimulation
The magnetic field is about the same strength as an MRI

So in the range  1 to 7 Tesla.

If you're planning on executing people with electricity there's far more cost-effective ways of doing it.
 

Offline Bored chemist

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Re: How much magnet does it take to kill?
« Reply #2 on: 16/03/2014 09:39:03 »
"Transcranial magnetic stimulation can cause seizures, and seizures can be fatal."
That's how much of a rate of change of magnetic field it takes to kill people.
In a homogeneous steady field I can't think of an obvious means by which the field would cause harm.

"can a strong enough magnet rip the iron out of your blood? "
No
Metallic iron is magnetic. Most of its compounds (including hemoglobin) are not.

A magnet that could produce a field of 1 Tesla over an volume the size of someone's brain would be so big and heavy that it would kill them if you dropped it on them. A big rock would be cheaper.
 

Offline ScientificSorcerer

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Re: How much magnet does it take to kill?
« Reply #3 on: 16/03/2014 09:46:42 »
interesting so only a rapid changing magnetic field can kill via magnetism alone, a constant magnetic field can't kill you? hmmm... cool just the answer I was looking for. thanks you guys.
 

Offline Aemilius

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Re: How much magnet does it take to kill?
« Reply #4 on: 16/03/2014 12:08:18 »

In a homogeneous steady field I can't think of an obvious means by which the field would cause harm.


Actually, steady homogeneous magnetic fields could be harmful if one were to pass through a series of them quickly enough. For example, flying low through a series of closely spaced homogeneous steady magnetic fields of alternating polarity on a plane full of jet fuel at around 900 miles an hour might cause transcranial magnetic stimulation to occur. Along with possibly affecting the avionics, the pilot could go into convulsions and the plane could even crash into a building....

 
« Last Edit: 16/03/2014 12:27:14 by Aemilius »
 

Offline Bored chemist

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Re: How much magnet does it take to kill?
« Reply #5 on: 16/03/2014 12:56:16 »

In a homogeneous steady field I can't think of an obvious means by which the field would cause harm.


Actually, steady homogeneous magnetic fields could be harmful if one were to pass through a series of them quickly enough. For example, flying low through a series of closely spaced homogeneous steady magnetic fields of alternating polarity on a plane full of jet fuel at around 900 miles an hour might cause transcranial magnetic stimulation to occur. Along with possibly affecting the avionics, the pilot could go into convulsions and the plane could even crash into a building....

 
If you had spent more time thinking about the meaning of homogeneous and less on drawing animated graphics, you would realise that any set of homogeneous steady magnetic fields that are adjacent to one another would have to be the same.
 

Offline Aemilius

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Re: How much magnet does it take to kill?
« Reply #6 on: 16/03/2014 14:51:25 »

If you had spent more time thinking about the meaning of homogeneous and less on drawing animated graphics, you would realise that any set of homogeneous steady magnetic fields that are adjacent to one another would have to be the same.


No, I don't think so Bored chemist. A single magnet can have a steady homogeneous (uniform, consistent) magnetic field, so a number of magnets can each have a steady homogeneous (uniform, consistent) magnetic field. For them to be homogeneously indistinguishable collectively they would all have to have the same polarity top and bottom down the line, but the polarity alternates so they are distinguishable from one another and hence not collectively homogeneous....



It's a series of alternating individually distinguishable homogeneous (uniform, consistent) magnetic fields.... Got it?   
« Last Edit: 16/03/2014 15:44:56 by Aemilius »
 

Offline Bored chemist

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Re: How much magnet does it take to kill?
« Reply #7 on: 16/03/2014 16:53:47 »
Do you really believe that a magnet has a homogeneous field?
Do you not realise that field falls off with distance so it isn't homogeneous?
So this "A single magnet can have a steady homogeneous (uniform, consistent) magnetic field, so a number of magnets can each have a steady homogeneous (uniform, consistent) magnetic field."
 is plainly wrong.

Seriously, more study, less cartooning.
 

Offline Aemilius

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Re: How much magnet does it take to kill?
« Reply #8 on: 16/03/2014 19:47:31 »

Do you really believe that a magnet has a homogeneous field?
Do you not realise that field falls off with distance so it isn't homogeneous?


Do you not realize that with the proper configuration (shape of the magnet, using pole pieces and/or other magnetic fields properly oriented in the vicinity) a single magnet can easily create an approximately homogeneous region (blue) within a magnetic field?



So this "A single magnet can have a steady homogeneous (uniform, consistent) magnetic field, so a number of magnets can each have a steady homogeneous (uniform, consistent) magnetic field."
is plainly wrong.



Just as a single magnet properly configured can approximate a region of homogeneity within a magnetic field, so too can a number of individual magnets properly configured approximate a series of such regions (blue) whose polarity alternates over time from the point of view of an object passing through them.


They're not cartoons by the way, they're called "Sche-mat-ics.... A sche-mat-ic, or sche-mat-ic diagram, is a representation of the elements of a system using abstract, graphic symbols rather than realistic pictures."

Do you understand sche-mat-ic Bored chemist?

 

« Last Edit: 16/03/2014 20:21:42 by Aemilius »
 

Offline evan_au

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Re: How much magnet does it take to kill?
« Reply #9 on: 16/03/2014 20:05:47 »
The somewhat salty solution in your bloodstream would act as a moving conductor in a static magnetic field. As blood circulates around your body, it would develop a small voltage across your blood vessels.

Since the cell walls are somewhat insulating, this probably won't result in much of a current. But since your body uses small electric fields to control cell growth and wound healing, it may have some impact in the long term. But you would probably suffer from cramps and DVT from being stuck in a tight magnetic coil for an extended period.

See a live frog, strawberry and others levitated in a 16T static field: https://www.ru.nl/hfml/research/levitation/diamagnetic/
 

Offline Bored chemist

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Re: How much magnet does it take to kill?
« Reply #10 on: 16/03/2014 20:20:17 »
"Do you not realize that with the proper configuration (shape of the magnet, using pole pieces and/or other magnetic fields properly oriented in the vicinity) a single magnet can easily create an approximately homogeneous region (blue) within a magnetic field?"
Yes.
Do you realise the significance of the bits I have italicised?
Have you noticed that your hypothetical plane will probably be just fine in those areas, but not in the areas where the field is heterogeneous?
Did you think you had raised a valid point?


Incidentally, I understand schematics well enough. They seldom need animation, but they do need proper consideration.
You, on the other hand,  failed to consider what would happen to your plane in the bits where the field was (as specified) actually homogeneous.


You might also want to think about the nature of electromagnetic induction.
In the areas where the field is near homogeneous, the plane is flying along the lines of flux.
What potential will be induced?


Perhaps  you should have spent more time thinking, and less time animating the cartoon.




In the limit, Avan's point is valid. It would cause a problem.
It would take one hell of a field to do it.

 

Offline Aemilius

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Re: How much magnet does it take to kill?
« Reply #11 on: 16/03/2014 21:36:59 »

Do you really believe that a magnet has a homogeneous field?
Do you not realise that field falls off with distance so it isn't homogeneous?
So this "A single magnet can have a steady homogeneous (uniform, consistent) magnetic field, so a number of magnets can each have a steady homogeneous (uniform, consistent) magnetic field."
is plainly wrong.


So first you say I'm plainly wrong....


Aemilius.... "Do you not realize that with the proper configuration (shape of the magnet, using pole pieces and/or other magnetic fields properly oriented in the vicinity) a single magnet can easily create an approximately homogeneous region (blue) within a magnetic field?"

Bored chemist.... "Yes."


....and then you say I'm plainly right!


Incidentally, I understand schematics well enough. They seldom need animation....


Apparently not well enough.... posting those "cartoons" got you to reverse yourself on whether a single magnet can approximate a region of homogeneity within a magnetic field.


You, on the other hand, failed to consider what would happen to your plane in the bits where the field was (as specified) actually homogeneous.


No I didn't, read it again. I said passing through the homogeneous portion could be harmful (there would be a series of rapid reversals of polarity between the homogeneous regions), not that it would definitely be harmful.


You might also want to think about the nature of electromagnetic induction.
In the areas where the field is near homogeneous, the plane is flying along the lines of flux.
What potential will be induced?


Know all about it. The plane would be at greatest risk as it passed over the poles where it would be cutting through the magnetic field perpendicular to the lines of force blah, blah, blah, blah....


Did you think you had raised a valid point?


Considering the topic is "How many Teslas do you need to kill someone?", it's good enough as an example of how both electronics and people might be adversely affected by passing through a powerful alternating series of static magnetic fields at a high rate of speed.
« Last Edit: 16/03/2014 23:39:29 by Aemilius »
 

Offline alancalverd

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Re: How much magnet does it take to kill?
« Reply #12 on: 17/03/2014 07:32:52 »
http://ec.europa.eu/health/scientific_committees/opinions_layman/en/electromagnetic-fields/l-3/8-static-fields.htm#2p0 is a good summary of current knowledge and is at best equivocal about any persistent effect of a static field up to several tesla.

Colleagues have exposed rats to 8T with no lasting effect and you'd have a heck of a job trying to make a homogeneous static field any stronger that could contain any useful part of a human.

The health effects of static fields derive from their spatial inhomogeneity  (making loose objects accelerate towards the patient in an MRI unit) or the associated RF electromagnetic radiation and timevariant magnetic fields used in MRI.

The effort and energy required to make a lethal static magnetic field, and to persuade someone to stand in it,  would be better devoted to generating an EMF that can fry the victim at a distance. Or a gun. 
 

Offline Aemilius

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Re: How much magnet does it take to kill?
« Reply #13 on: 17/03/2014 15:19:59 »


Colleagues have exposed rats to 8T with no lasting effect and you'd have a heck of a job trying to make a homogeneous static field any stronger that could contain any useful part of a human.


Right, static fields present no obvious health risks.... not susprising really since all life evloved in one.


The health effects of static fields derive from their spatial inhomogeneity  (making loose objects accelerate towards the patient in an MRI unit) or the associated RF electromagnetic radiation and timevariant magnetic fields used in MRI.


Swallowing them can be a problem.


The effort and energy required to make a lethal static magnetic field, and to persuade someone to stand in it,  would be better devoted to generating an EMF that can fry the victim at a distance. Or a gun.


Exactly. You'd probably need the magnetic equivalent of a Black Hole and you'd have to be able to focus/direct it as well.... just to levitate a mouse at twenty feet! 
« Last Edit: 17/03/2014 15:57:29 by Aemilius »
 

Offline Aemilius

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Re: How much magnet does it take to kill?
« Reply #14 on: 17/03/2014 16:04:39 »

....would be better devoted to generating an EMF that can fry the victim at a distance. Or a gun.


We don't really have any other type of practical "Beam Weapon" besides the high powered laser do we Dr. Calverd?
« Last Edit: 17/03/2014 16:06:12 by Aemilius »
 

Offline Aemilius

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Re: How much magnet does it take to kill?
« Reply #15 on: 17/03/2014 16:41:35 »
 

Offline evan_au

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Re: How much magnet does it take to kill?
« Reply #16 on: 17/03/2014 18:11:01 »
Quote
Right, static fields present no obvious health risks.... not surprising really since all life evolved in one.

The strength of Earth's magnetic field at the surface ranges from 25 to 65 microTesla.

It's a bit of a stretch to extrapolate from 65 microTesla to health effects at 1-16T.
 

Offline Aemilius

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Re: How much magnet does it take to kill?
« Reply #17 on: 17/03/2014 19:07:07 »
Quote
Right, static fields present no obvious health risks.... not surprising really since all life evolved in one.

The strength of Earth's magnetic field at the surface ranges from 25 to 65 microTesla.

It's a bit of a stretch to extrapolate from 65 microTesla to health effects at 1-16T.

Agreed. I guess like most people I always just assumed they (static fields) were harmless, but that article Dr. Calverd posted does show some interesting long and short term effects like....

"Behaviour of rats was studied by Houpt et al. (2007a, b). In their first paper the animals were trained to climb though the bore of a sham NMR unit (large vertical magnet). When this was switched for a real magnet with a field strength of 14.1 T, half of the animals avoided climbing into the magnetic field. Upon further testing the animals had already stopped climbing at a field strength of about 2 T."

....and even some residual effects....

"Ammari et al. (2008b) exposed mice to a 128 mT SMF for 1 h/d, 5 d. No effect on anxiety was observed, but the mice developed an altered emotional behavior and cognitive impairment."

....so it could just be that static magnetic fields interfere with more and more processes as field intensity increases, maybe at some threshold intensity critical functions (heartbeat, respiration, etc.) could be impaired, or maybe it could even cause long term behavioural or cognitive impairment as with the mice.  But like Dr. Calverd said earlier "....you'd have a heck of a job trying to make a homogeneous static field any stronger that could contain any useful part of a human." so we probably won't know anytime soon.
   


« Last Edit: 17/03/2014 19:20:00 by Aemilius »
 

Offline Bored chemist

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Re: How much magnet does it take to kill?
« Reply #18 on: 17/03/2014 22:06:33 »

Do you really believe that a magnet has a homogeneous field?
Do you not realise that field falls off with distance so it isn't homogeneous?
So this "A single magnet can have a steady homogeneous (uniform, consistent) magnetic field, so a number of magnets can each have a steady homogeneous (uniform, consistent) magnetic field."
is plainly wrong.


So first you say I'm plainly wrong....


Aemilius.... "Do you not realize that with the proper configuration (shape of the magnet, using pole pieces and/or other magnetic fields properly oriented in the vicinity) a single magnet can easily create an approximately homogeneous region (blue) within a magnetic field?"

Bored chemist.... "Yes."


....and then you say I'm plainly right!


Incidentally, I understand schematics well enough. They seldom need animation....


Apparently not well enough.... posting those "cartoons" got you to reverse yourself on whether a single magnet can approximate a region of homogeneity within a magnetic field.


You, on the other hand, failed to consider what would happen to your plane in the bits where the field was (as specified) actually homogeneous.


Nice try.
However I said you were wrong about one thing
"A single magnet can have a steady homogeneous (uniform, consistent) magnetic field"
but right about another
"a single magnet can easily create an approximately homogeneous region"
Because one of them specifies homogeneous, and the other specifies approximately homogeneous.

They are not the same thing, especially since it's the inhomogeneity that will kill you quickest.

So, stop pretending they are the same thing.
And, obviously this bit
"Apparently not well enough.... posting those "cartoons" got you to reverse yourself on whether a single magnet can approximate a region of homogeneity within a magnetic field." makes no sense once you realise there was no reversal.

However, if we are talking about reversals, I see you now agree with what I said in the first place
"Right, static fields present no obvious health risks.... not susprising really since all life evloved in one."

Albeit- right for the wrong reasons.


« Last Edit: 17/03/2014 22:10:18 by Bored chemist »
 

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Re: How much magnet does it take to kill?
« Reply #18 on: 17/03/2014 22:06:33 »

 

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