MRI MAGIC

[areneephoto]

However, it is 20,000 times stronger than the earths magnetic field. Powerful eyes. Please, do not have one if you have metal in your eyes O_O

[areneephoto]

MRI is a magnet composed of 3 gradients (smaller magnets). A screw will not shoot out of your body unless made of solid metal and in soft tissue without healing. Come on....

[SmallShielsy]

It's like magic! how does it work?

[BabiaaLiseia864]

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[killerbeenl]

That is just eddy currents (might be spelled incorrect) look it up on YouTube if interested further. There is a power running trough the conductor (aluminium) what causes the currents in the conductor "fighting" its own movements. (back emf.) Non magnetic materials can give back their inducted loads like on this example. The coper tube and magnet trough it is a nice test for home.

[ladyblackmour]

To quote xkcd..."Stand back! I'm going to try science!"

[justinp2416]

That is a piece of aluminum. I work around MRI's for a living If that was steel it would have been sucked before that guy could put it down.

[ShinobiBoiX]

...because science.

[junkdeal]

If that block was iron, what a speeding bullet it would've been!!

Try this neat experiment. Take a "neob" magnet, maybe 1 inch round 1 inch long, and drop it down a copper pipe. It takes a long time to fall through. Induced EMF fights it. Just like a generator with a load, Now slit the pipe open (one cut down one side) and mag falls right through. now wire a galvanometer to each side of the slit, drop mag, and you get a volt reading. The unslit pipe is a connected load, thus the back EMF!

[Ortmoon]

This simple video made me understand Lenz law:) Thanks!

[HerDarkestHour]

I'm not a carpenter but that is definitely a bad idea

[plasmasun]

So Fucking Dope!

[leavingjupiter]

WIZ722 is right. You are seeing the effects of eddy currents in a non metalic metal.

You can see this at home if you take a supermagnet, and let it slide across a heavy aluminum frypan. The steeper you tilt the pan, the more you will see the effect of the eddy currents in the pan opposing the movement of the magnet.

[ParkourIvan]

@leavingjupiter non metalic metal FTW

[wiz722]

I'll explain The block is NOT magnetic. It looks more like aluminum, but whatever it is, it is NOT MAGNETIC because if it were, it would go flying through the MRI machine. (search for how strong is an MRI magnet). Instead, the magnetic field induces eddy currents on the block which oppose the force of gravity, but not enough to stop it from falling. LOOK UP EDDY CURRENTS.

[Toshibasan]

good explanation

[trustthewater]

Same (looking) thing happens if you knock over a spinning hard drive...

different forces and lose of data, but it looks similar.

[simpleau2]

@trustthewater

I think it has more to do with spinning inertia then with magnetic fields. They had this great experiment on the ISS with CD readers and a flashlight to show how you could use a spinning load to stabilize a system. In the case of the hard drive, the mass of the plates rotating gives makes the whole thing a gyroscope, hence why it resists being tilted when you push it over.

[ExNihiloJimmy]

magic? It's fucking magnetism

[Jenfucius]

I wonder what would happen if mercury was placed in an MRI?

[TheShawMaestro]

Nothing. Mercury is not magnetic.

[xion101]

Neither is aluminum you idiot. An MRIs field strength is about 3T, trust me, you dont want to put anything magnetic near that....

[TheShawMaestro]

What? Idiot? Who said anything about aluminium?

[metamaterial]

Interesting. Like Shaw says, not much could be seen if it wasn't moving. I think if you put it on, say, a piece of glass and moved it back and forth it would resist the movement a fair bit.

[roidroid]

@metamaterial it could look interesting if you poured the mercury down something - it might pour in slow motion.

[metamaterial]

@roidroid Though you might want to be less deadly and use something like Woods' metal for the experiment, I think it would work. ^ ^

[Lightningchase1973]

Sorry, Mr. Happy Cynic, but you're description has a major fault. These magnets will only rip FERROMAGNETIC screws out of youzr body, not metal srews (od other implants) at all. Usually impkants are not made out of ferromagnetic materials since a while. Due to eddy currents, the movement of any metal is slowed down (and heating it up somewhat), but a pulling force is only applied to ferromagnetic metals. A big difference.

[Vexracingsports]

i just got an MRI today that crap was so damned lud

[gcmsboy1234]

You could have been hurt. If the metal was less heavy and the magnet was stronger it could have pulled the metal and crushed your hands.

[Mednovotob]

Not all metals are attracted to magnets, only alloys of Iron, Nickel and Cobalt. This means most steels and the metals in most batteries (plus a host of other things). Aluminum, Titanium, Brass, Copper, Zinc, and many others aren't magnetically attracted.

However, all electrically conductive materials (like metals) are subject to the Lenz effect, which is what you're seeing here. Essentially, a conductive material in a magnetic field becomes resistant to motion by counter fields.

[Jenfucius]

Would something like mercury be effected by the Lenz effect???

[Mednovotob]

Lenz effects will apply to anything that is an efficient electrical conductor. Mercury certainly is that! But since it's not solid, it'd be a very interesting experiment to see just how the physical Lenz forces manifest themselves... great question.

[Jenfucius]

Thanks Mednovotob.

[westkan]

A stionary magnetic field from the machine wouldn't induce a magnetic field around the metal, but the changing field would. The fields must be attacking each other, reducing gravities force that pulls the block down. The same concept as the magnet slowing falling down a copper pipe. Took me a bit of pondering to figure out, how the induced field was coming from the machine, until I read the wiki article on the mri machines.

[westkan]

Evidently a MRI machine in operation produces a magnetic field that's in motion. That creates a current in the AL block, and that current produces a magnetic field surrounding the AL block, and it's the interaction of the magnetic fields that allows the AL block to fall slowly. Not that I know for sure, but that's the only way I can make sense of it.

[Retsam19]

Ya is most likely, or the magnetic field could be stationary because he has knocked the block over, so the magnetic field would then move relative to the box as it is falling. But i think the magnetic field in MRI keeps changing, think that is why they make those banging noises. It's contraction of metal caused by a varying field.

[anschel1010]

yeah, "magnetstricture", makes the humming noise in transformers, mris and other ac electromagnets, when magnetic fields go through a core (block) of metal and make its atoms vibrate at the frequency of the magnetic field (humming)

[sitnavel]

not true. bad transformers don`t fix the solenoids tight enough, so they start vibrating. carefully made, transformers don`t buzz. I`ve got 2 non-buzzing transformers at home, and another one which is kept buzzing quietly with a piece of wood sticked between the solenoids.

[ccsue12]

Lenz's Law!! YAY!!

[wisteela]

Cool.

[dLimboStick]

I've had a chance to play with an MRI. We used to see how many paper clips we could connect and make float in the air. We got it up to about 6 feet long. Good times.

[inagod]

I never get asked if I have any metal in my body,99 percent don't,so most techs get very comfortable not asking,assumming someone else will catch it..accidents still happen

[SarahxJane]

That's awesome.

[bestSVMS]

rub a hd magnent on a brand new roll of aluminium foil, and you can feel lots of resistance

[jaymcq93]

its fake...he put it in slow motion..thats why you dont hear the sound when the aluminum tips over

[DigiTan000]

Nah, it's Lenz's Law in action. The falling motion induces an Eddy current in the block. That current has its own opposing field (via Biot-Savart's Law) that slows the fall. The new trains are using this for braking these days.

[jaymcq93]

o really ..thanks for telling me that...i didnt know the science behind it

[kathryn120]

Do you think MRI's are safe? I mean, do you think there are any negative effects toward people?

[redcrowdesign]

They are safe for the patients, it doesn't use ionizing radiation, however, high dosis of magnetism on daily basis could damage the cells and cause cancer. I think that would take a long time tho.

The only real risk here is if you got a metalic item on you.

[Mednovotob]

If your theory were true, then why don't we see huge cancer rates in the Technologists / Radiographers who work around these machines every day of their working lives?

[DigiTan000]

Yep. To date I've only read of 2 *rare* side effects.

1. One the scanning antenna's *very unlikely* failure modes could cause a burning pain. Nicotine patches are also known to gain heat from the scanning field.

2. Some people temporarily saw dim, streaking lights in their vision while in the fixed field (maybe due to the pull on Ca+ ions in the ocular nerve). This I haven't verified.

But they're much safer long-term than XRay, CT, or PET. If ever in doubt, you can also contact the FDA.

[bestSVMS]

lenz law

science at work

pretty cool

[laggist]

nice landing!

[qsucvatz]

Eddy currents.

[theinsane101]

antigravity

[forsbrookme]

ha antigravity

what a nub

[PostTheMissing]

The aluminum is NOT magnetic. When the aluminum is placed into a magnetic field its creates a flow of electrons that make an electromagnet that REPELS the magnetic field entering it, so it falls very slowly. The flow flow of electrons creates friction as they flow, and thats why it heats up and DOESNT FLOAT. However, there are superconductors that dont produce any friction(or very low friction at least) and they do float, so check out some videos about that.

Hopefully that can help someone out

[sirgimpofbaath]

A small addendum: superconductors actually have NO resistance at all, not small resistance. It's a quantum thing.

[Hypermobilemind]

Omfg, thank you for explaining this, i checked on wiki for lenz's law, but i can never understand their explanations, i thought it would be something like that.

You can also build mass launchers using this principle, and they can shoot projectiles in an aluminum holder at incredibly fast speeds.

Do you know of any other materials other than aluminum that have this characteristic that makes them repel magnetic fields?

[PostTheMissing]

Bismuth, Mercury, Silver, Water, Carbon(diamond)

Carbon (graphite), Copper, Lead.

There might be more.

[Hypermobilemind]

thanks

[sciencoking]

actually everygood non-magnetic conductor can do this. Copper is fantastic to make an example because it´s quite cheap and has a very low specific resistance. try it yourself: take an HDD magnet and let it slide down a copper sheet. You´ll notice that the fall is really slow, also when you hold the copper almost vertical. it´s amazing...

[duckythescientist]

It is not that aluminum repels magnets here but that aluminum is conductive. In this experiment, anything conductive and nearly non ferrous would work.  You are thinking of something else.

[Hypermobilemind]

yeah its the way the MRI machine affects the free electrons in the aluminum right?

[duckythescientist]

Yes, same with all things conductive.

[cyberrigger]

Aluminum is not ferromagnetic.

Aluminum is paramagnetic and it is weakly attracted to a strong magnet.

[bustaphatty]

@PostTheMissing lies, its God slowly lowering it.

[TheWartHawg]

@PostTheMissing Just as a point of clarification, a material that repels magnetic field lines is classified as diamagnetic. Aluminum is paramagnetic, so it demonstrates a very weak magnetic attraction.

[Preci0usKitten]

What the poster of this video failed to mention is that the "solid hunk of metal" pictured is actually a solid block of ALUMINUM, which itself has very minimal magnetic properties (try sticking a magnet to a soda can). The fact that the MRI so profoundly affects the rate of fall of this non-magnetically responsive piece of metal is testament to the incredible power of the magnetic field it creates...

w00t.

[Symphyla]

gravity wins!

[Youmarge]

All MRI are magnetic even if they aren´t in use. The inductor is subraconductin. So it conduct electricity and produce a megnetic field, even if you don´t connect it to a powersource.

[godthegourd]

all mri's are magnetic! it comes in the name! if you have a 1 inch wood screw in 3 inches of pinewood and you secured it inside a moving mri the screw would come out of the wood at around 800 miles per hour. wow.

[pyrokiddownthesreet]

kick ass

[Fointy]

i want to see them just drop it from a height in the machine. Watch it fall slowly through the air.

[foxhound75]

Correct me if I am wrong but if you just drop it, wouldn't the eddy currents cancel themselves out and it would fall like normal?

[floodtl]

Cool.

[wesmess14]

On the Moon, nerds get their pants pulled down and they are spanked with Moonrocks.

[monka6]

kinky.

[Thissiteisapain]

I like your line of thinking!

[svensktigre]

pay homage to the great space ape- no drop them sweat pants!

[scoobyrex02]

First off, thats probably aluminium or some semi-ferrious material. Reason it falls slow like that is due to the Magnets eddy currents.

also, most magnets will not pull a screw out of your body. I wouldn't doubt it would be painful, but don't know since I don't have any ferrious material in me. But work around Magnets regularly. Still wouldn't suggest going near one or definatly wouldn't get scanned if you have metal implants.

[STICKSnSTRINGS]

99.9% of all bullets are non-ferrous, and therefore would not respond to the pull of the MRI. However if you have metal in your body, As i understand it could possibly become heated during an MRI due to RF energy

[BarneySaysHi]

You say it can "pull a metal screw out of your body like a bullet shot". Does that mean that the episode of House where he extracts a bullet from a corpse with the MRI, subsequentally destroying the MRI in the process, isn't fiction at all?

[conoba]

A neodymium magnet is nothing compared to that.

[Ouendanman64]

Can a Neodymium magnet attract a tennis ball?

[docprocto]

just ferromagnets objects like Iron

[AJFishdude20X6]

Whether or not gravity or magnetism is stronger simply has to do with the power behind the force. The force of gravity on an object for the most part has to deal with the mass of the object (like the Earth) and your proximity to the center of mass of that object. Magnetism has to do with how polarized a magnet truly is, or in the case of electromagnetics, how powerful of a current is run through the magnet.

[elgranto7]

9.8m/s-1 baby

[broken121589]

A block of Aluminum and Eddy Current

[VideoJunkei]

so if you tried to move that block around that magnet, it would resist? Would it fall slowly through the air if dropped?

[urospiperski]

Yes, it resists the motion. It will fall slowly if it's oriented in a proper way to the field lines and is dropped inside the magnet bore.

The gravity is still stronger :)

[jasondubose2007]

actually i think there aren't too many people that would say that gravity is a stronger force than magnetism. The resistance comes from eddy currents.  it continues to fall not because gravity is stronger, but because the eddy currents are a function of changing magnetic field. if there were no movement, there would be no resistance....and the orientation is neglegible too.

[starkstromfunker]

Just working on non-ferromagnetic metal.

Aluminium or V4A...

[kimager]

The tattoo question is actually a good one.

It is not unknown for *some* tattoos to contain metallic inks. Although perhaps not ferromagnetic, in certain MRI sequences these can *potentially* heat up and cause swelling/burns. The clinical reports appear to be very rare, but it is a real phenomena.

Googling "MRI tattoo" is worth a look.

So if you are having a scan, the Tech may well ask you about tattoos and it is worth telling them about any you have.

[bigboioncrack420]

hey im geting an mri soon and i have a tattoo.whats gona happen

[sebijproductions]

Is the tattoo out of ferromagnetic material?

I don't think so, so nothing is going to happen!

[skimboley]

you can actually do this with a coke can - WARNING take nothing in the room unless you are SURE (test it first!) that it is not magnetic --- remember the most important thing the magnetic is ALWAYS on

[mrbonaparte]

I always wondered what would happen if you threw a penny at an MRI

[pitbullo]

Nothing would happen. Coins are not magnetic.

[elgranto7]

english pennys are

[pauliogazzio]

some are, not all are, i think its the newer ones are non-magnetic....

[elgranto7]

yeah its weird

[frizspin175]

but mri stands for magnetic resonance imaging, so what would they call it?

[thermoid]

umm...ALL ARE MAGNETIC

[danh4321]

M = Magic.

[trebor166]

Even dumber is you taking the time to show your ignorance.

[g105b]

idiots like that make my blood boil. so does gas mark 5.

[wbeaty]

In a 1989 newsletter from AZ Magnetics, they described just this phenomenon, but in their version they were dropping an aluminum slab onto the pole face of a huge neodymium supermagnet. (AZ Magnetics were in the business of building non-cryo MRI magnets, huge permanent magnets made by gluing 7" supermagnet bricks together in solid arrays.

[ctstan911]

you can actually do this with a coke can - WARNING take nothing in the room unless you are SURE (test it first!) that it is not magnetic --- remember the most important thing the magnetic is ALWAYS on!!

Good luck with your training ---- not wanting to sound anal but I would hate for someone to kill themselves not understanding the magnet nor would I want someone to not get a test they needed because they were scared to get near it.

peace

[TheHappyCynic]

Thanks for those clarifications and warnings. Yeah, I am still only in the classroom phase of my training, but I am excited, so thanks for the encouragement as well.

[ctstan911]

glad you're studying to be a biomedical tech. I have been an MRI tech for the last 20 years - you will NOT have a metal screw fly out of you body like a bullet. you can however cause it to move around (if it is made of ferromagnetic material) or possibly heat up. what you are seeing on the video is called eddy currents -this is metal not attracted by the magnetic (or it would have flown out of their hands) but rather is light enough to be effected by the "currents" of the magnetic field.