Magnetic field and how it is dangerous - Page 1
Forum section: electronics / beginners

author: Roberto Kun
author_rank: Newbie
timestamp: April 03, 2023, 12:50:07 am
content: My question is about magnetic fields and their relation to health. I intend to buy a product on AliExpress that uses a magnetic field generator to keep a decoration suspended in the air. However, I am concerned that the magnetic field required for this may be so strong that it could be harmful to the health of both adults and children. I would like to know if anyone can tell me the intensity of the magnetic field of this item and if it poses any danger to the health of adults and children. Here is the link:https://pt.aliexpress.com/item/1005004883829701.html?spm=a2g0o.ppclist.product.4.f15aRNQ1RNQ1Qa&pdp_npi=2%40dis%21BRL%21R%24%20879%2C64%21R%24%20457%2C39%21%21%21%21%21%402101f6b616804818376522699e3157%2112000030882977553%21btf&_t=pvid%3A60582d38-9ce6-4c52-8a4b-07090d3ee17a&afTraceInfo=1005004883829701__pc__pcBridgePPC__xxxxxx__1680481837&gatewayAdapt=glo2bra

author: jonpaul
author_rank: Super Contributor
timestamp: April 03, 2023, 02:54:15 am
content: Fileld is not a medical issue, device is cheap junk, hardly worth it.Search magnetic suspension, DIY, you,will learn a lotJon

author: DrGeoff
author_rank: Frequent Contributor
timestamp: April 03, 2023, 03:05:55 am
content: Do you realise that high-intensity magnetic fields are used in MRI scanners?

author: py-bb
author_rank: Regular Contributor
timestamp: April 03, 2023, 03:08:42 am
content: Quote from: Roberto Kun on April 03, 2023, 12:50:07 amGet a paperclipbut make sure it's a steel one and sticks to magnets!, put it in your pocket. If you can feel a force on at all you forgot to take it out of your pocket before getting an MRI.The risk to your health then is the paperclip.

author: radiolistener
author_rank: Super Contributor
timestamp: April 03, 2023, 03:41:53 am
content: Usually if field strength doesn't lead to a thermal damage and doesn't exceed safety limits it is considered safe for a short period of exposure. But for a long period of exposure things are different, it's effect on health is unknown,some research shows that it potentially can be dangerous, but there no 100% evidence for safety or danger, because this is too complicated thing for research and result may depend on a lot of different factors (such as field strength, frequency modulation waveform, presence of other factors, etc).In a short, I think if you play with it for a short period of time (let's say 1-2 hours) it is probably safe. But if you're planning to exposure your body 24/7, nobody knows how it can affect your health... It can lead to a cancer or other diseases after some period of time, but nobody knows how long it will take and what consequences is possible, it depends on many factors. For one people it can be safe for years, for other it can lead to some disease even with low field strength exposure.Regarding to the device from your link. I wouldn't use this at home for even a few minutes, as you can see it has filament glowing, these filaments needs pretty high voltage. So, it means that there is extreme high RF field strength, especially E component. I think it's more than 1 kV/m. I played such field strength in the past (magnetic loop antenna + transmitter), but then decided to avoid it. Because it is exceed safety level and can affect your health.In addition, such device has a very high RF emission at random frequency, which is not allowed by FCC. So, if you use such device it can affect RF communication and medical devices in your area which is not legal and if it happens you will have serious problems with law.

author: coppercone2
author_rank: Super Contributor
timestamp: April 03, 2023, 05:21:38 am
content: this happens

author: MrAl
author_rank: Super Contributor
timestamp: April 03, 2023, 06:29:42 am
content: Quote from: Roberto Kun on April 03, 2023, 12:50:07 amHello there,I do not have any direct information on how a magnetic field affects health, but i do know some related facts and one in particular come to mind.That is the fact that a CHANGING magnetic field causes electrons to move, flow if you will. That constitutes an electric current even though the electrons are not inside a wire. There could be a little more randomness to it, but the electrons will move.Electrons moving can cause heating, and heating can 'cook' just about anything. So in theory, a changing magnetic field can cause small currents to flow inside your body which can cook cells, or at least heat them up. That's something i would not want inside my body.The nice thing is that distance plays a very important role in this effect. The farther you are away from the magnetic field source, the less the effect, and the effect goes down fast with distance. For a quick example, if you are 2 inches from the source and are affected by the magnetic field, if you move 4 inches away (twice the distance) the effect drops to 1/4 of the original effect. If you move 8 inches away, the effect drops to just 1/16 of the original effect. So the effect drops off pretty fast, meaning much less current flow at increasing distances. This of course means that if you stay away from the source you would be ok for the most part.As others have said though, keep the time of the exposure low also. That reduces the effect in proportion to the time, so if you are exposed for 8 seconds and are affected by a certain amount, but instead are exposed for 4 seconds (1/2 the original time) the effect is reduced to 1/2 of the original, and if you are exposed for just 2 seconds (1/4 of the original) then the effect is 1/4 of the original.So the effect drops with the square of the distance, and in proportion to the time of the exposure. Increasing the distance and decreasing the time reduces the effect and therefore the possibly health concerns. Of course it does increase with the field strength of the source.One thing i remember from way back. There was an experiment done on a frog with a very very very high strength, controlled magnetic field. The frog was levitated just like in the picture of the light bulb. This was a living frog though. It did not seem to be affected but i do not know if they did an autopsy later to determine if any nerve damage, organ damage, or cell damage had occurred. I do know the frog was still alive though because it could still move around. While in the field it did not go crazy though, like start moving the legs rapidly as if trying to get away, so i dont think it experienced any pain, but of course i cant be sure about that.So the final work i believe is keep the exposure time short and dont get too close and you should be ok. Personally though i think it is a huge waste of money. You'll look at it once or twice, people that come to visit will look at it once or twice, maybe three times, then go about their business. They might say, "Oh, that was cool", then walk away, but that's probably all that will come of this.You know what they say though, "It's your money, use it when you need it". (chuckle).

author: Manul
author_rank: Super Contributor
timestamp: April 03, 2023, 02:37:35 pm
content: It may cause some EMI for sensitive equipment like medium wave radio receiver. Regarding health effects, I believe it to be zero. Call me what you want, but I have never had any fear when dealing with magnetic or EM fields. I don't know of any serious evidence that it has an effect.

author: TimFox
author_rank: Super Contributor
timestamp: April 03, 2023, 03:42:57 pm
content: MRI machines use three different types of magnetic field (over-simplified description):1. The "static" field is very strong, typically 1.5 T from DC in a superconducting coil.2. The "gradient field" is a collection of pulsed fields that encode position by making the local B field a function of position. The loud mechanical noise heard by the patient is caused by the force on the coil assemblies from the reaction between the gradient field and the static field.3. The "RF field" (which isnotradiation, but a B field that varies at radio frequencies, 64 MHz for 1.5 T static field) is used to excite the resonant effects in the magnetic moment from hydrogen nuclei.The gradient and RF magnetic fields, being time-dependent, will induce an E field (voltage gradient) in the patient and heat tissues by inducing eddy currents in the conductive saline content therein.Both of those effects are limited by health regulations; the latter is measured as SAR (energy dissipated per mass of patient).The static field does not induce voltage nor dissipate energy, but is extremely strong.Obvious problems include forces on ferromagnetic surgical implants and interference with cardiac pacemakers.Less obvious problems include MHD effects due to physical motion of the patient or parts thereof in the magnetic field: seehttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC4409466/1.5 T is a huge magnetic field: the Earth's field at the surface is roughly 50 nT (depending on location).

author: BravoV
author_rank: Super Contributor
timestamp: April 03, 2023, 04:02:46 pm
content: Watch this and be free ...

author: Simon
author_rank: Unknown
timestamp: April 03, 2023, 05:20:32 pm
content: spammer banned.

author: py-bb
author_rank: Regular Contributor
timestamp: April 04, 2023, 04:13:20 am
content: Quote from: Simon on April 03, 2023, 05:20:32 pmWho got banned? BravoV I think was just trying to be funny rather than promote something?

author: MK14
author_rank: Super Contributor
timestamp: April 04, 2023, 04:20:48 am
content: Quote from: py-bb on April 04, 2023, 04:13:20 amRoberto Kun apparently got banned, who started the thread (OP), as they seem to be a spammer (advertising links) spreader.

author: py-bb
author_rank: Regular Contributor
timestamp: April 04, 2023, 04:40:07 am
content: Quote from: MK14 on April 04, 2023, 04:20:48 amIn his one post?Given he's worried about magnetic field is it not possible the guy was stupid and (in presumably deleted messages?) going "well what about this product then why does it exist?"

author: radiolistener
author_rank: Super Contributor
timestamp: April 04, 2023, 03:23:56 pm
content: Magnetic field is not the thing that's need to be worry about in this device. Very high strength of RF near field is the issue of this device. It is used to transfer power into filament leds, but at the same time it affects any body in short distance from the device and it produce high RF emission which can lead to a medical device failure and even death (for example if people has cardiac implant). Also it produce a high interference on a floating frequency which can break some communication like aviation band and other which is not legal.Regarding to effect on the health. It doesn't produce immediate effect on health, because it has not enough power to damage people body with thermal heating. But long time exposure of such device can cause other negative effects on your health, such as cancer, physiological or mental disorders. But it depends on many factors, such as time of exposure, power, frequency, waveform modulation, your body state and many other things. So, it looks safe for testing for minute or two, but longer use it's on your own risk.

author: Simon
author_rank: Unknown
timestamp: April 04, 2023, 06:54:24 pm
content: Quote from: py-bb on April 04, 2023, 04:40:07 amThe AI in my head determined that it was spam. My AI has a 6th sense for this, not that I know how it works myself

author: Terry Bites
author_rank: Super Contributor
timestamp: April 04, 2023, 09:15:27 pm
content: I survived 2.4T and had all my protons pinged.Didn't even sting. F**kd up my credit card though.Shouldn't have slipped it in my jocks.

author: TimFox
author_rank: Super Contributor
timestamp: April 04, 2023, 09:25:26 pm
content: I worked in MRI when it was quite new.I attended a technical meeting in New York, and one desk clerk at the hotel was surprised at how many American Express cards presented at check-in had their magnetic strip messed up.

author: Simon
author_rank: Unknown
timestamp: April 07, 2023, 12:48:14 pm
content: there was that time in I think the 70's when a medical machine that produced radiation was malfunctioning and killing people.

author: Zero999
author_rank: Super Contributor
timestamp: April 07, 2023, 01:10:51 pm
content: Quote from: Simon on April 04, 2023, 06:54:24 pmThen that would be NI. Why didn't you delete the link if it's spam?

author: MK14
author_rank: Super Contributor
timestamp: April 07, 2023, 01:40:16 pm
content: Quote from: Zero999 on April 07, 2023, 01:10:51 pmThat is a good question. But since a number of replies to the thread, came about. Removing that link, would sort of damage the original source of information. So leaving the link, might be the best compromise.

author: Infraviolet
author_rank: Super Contributor
timestamp: April 07, 2023, 01:55:00 pm
content: Magnetic fields drop off very quickly with distance, inverse cube, a field strong enough to levitate something small within a tiny region is negligible out at the distance where your body is. Not that typical mag fields are a danger to health anyway.

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2023, 03:11:48 pm
content: Quote from: Simon on April 07, 2023, 12:48:14 pmYou’re likely thinking of the Therac-25 incidents, where really badly written software allowed a skilled (read: fast) operator to trigger a race condition that resulted in the machine being mechanically in a different configuration than the software thought it was, causing it to administer massive overdoses of ionizing radiation before throwing an error. (The error itself not indicating that anything had happened, so they’d try again…)Nothing to do with the magnetic fields in an MRI, of course.

author: TimFox
author_rank: Super Contributor
timestamp: April 07, 2023, 03:30:35 pm
content: Quote from: tooki on April 07, 2023, 03:11:48 pmThe Therac-25 is an example of radiotherapy equipment, where ionizing radiation is used instead of a scalpel to kill unwanted (i.e., cancerous) tissue.Specifically, it used an electron linear accelerator to make a beam of electrons, up to 25 MeV kinetic energy, that could be used directly or to generate photons (x rays) by hitting a tungsten target (Bremsstrahlung).Just like a scalpel, the high-energy ionizing radiation must be controlled very carefully, both in quantity and location.

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2023, 04:38:16 pm
content: Yes, I’m fully aware of all of that, I’ve read into the incidents in detail.