Home |
Search |
Today's Posts |
|
Home Repair (alt.home.repair) For all homeowners and DIYers with many experienced tradesmen. Solve your toughest home fix-it problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
More about magnetism and MRI's
It came up here wrt my planned MRI that there seemed to be things not made out of iron that were subject to magnets. By coincidence I came across this. From Wikip ... http://en.wikipedia.org/wiki/Ferrite_core Ferrites Ferrites are ceramic compounds of the transition metals with oxygen, which are ferromagnetic but nonconductive. Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. So I guess all these compounds and maybe more (that aren't used commericialy or not in transformers) would be magnetic like iron, but not containing iron, and to top it off, nonconductive. What a complicated world we live in, where there are general rules and exceptions to the rules. Nowadays, people are most likely to see ferrite cores as the small cylinders near the end of electric wires, such as USB cables, power supply adapter cables, etc. "hey have a low coercivity and are called "soft ferrites" to distinguish them from "hard ferrites", which have a high coercivity and are used to make ferrite magnets. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. The most common soft ferrites a Manganese-zinc ferrite (MnZn, with the formula MnaZn(1-a)Fe2O4). MnZn have higher permeability and saturation levels than NiZn. Nickel-zinc ferrite (NiZn, with the formula NiaZn(1-a)Fe2O4). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1 MHz. " |
#2
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
On Mar 2, 7:14*am, micky wrote:
More about magnetism and MRI's It came up here wrt my planned MRI that there seemed to be things not made out of iron that were subject to magnets. *By coincidence I came across this. From Wikip ...http://en.wikipedia.org/wiki/Ferrite_core Ferrites Ferrites are ceramic compounds of the transition metals with oxygen, which are ferromagnetic but nonconductive. Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. So I guess all these compounds and maybe more (that aren't used commericialy or not in transformers) *would be magnetic like iron, but not containing iron, and to top it off, nonconductive. What a complicated world we live in, where there are general rules and exceptions to the rules. Nowadays, people are most likely to see ferrite cores as the small cylinders near the end of electric wires, such as USB cables, power supply adapter cables, etc. "hey have a low coercivity and are called "soft ferrites" to distinguish them from "hard ferrites", which have a high coercivity and are used to make ferrite magnets. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. The most common soft ferrites a * * Manganese-zinc ferrite (MnZn, with the formula MnaZn(1-a)Fe2O4). MnZn have higher permeability and saturation levels than NiZn. * * Nickel-zinc ferrite (NiZn, with the formula NiaZn(1-a)Fe2O4). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1 MHz. " Magnetic fields are also associated with any electric current. |
#3
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
On Sat, 02 Mar 2013 02:14:48 -0500, micky
wrote: More about magnetism and MRI's It came up here wrt my planned MRI that there seemed to be things not made out of iron that were subject to magnets. By coincidence I came across this. From Wikip ... http://en.wikipedia.org/wiki/Ferrite_core Ferrites Ferrites are ceramic compounds of the transition metals with oxygen, which are ferromagnetic but nonconductive. Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. So I guess all these compounds and maybe more (that aren't used commericialy or not in transformers) would be magnetic like iron, but not containing iron, and to top it off, nonconductive. What a complicated world we live in, where there are general rules and exceptions to the rules. Nowadays, people are most likely to see ferrite cores as the small cylinders near the end of electric wires, such as USB cables, power supply adapter cables, etc. "hey have a low coercivity and are called "soft ferrites" to distinguish them from "hard ferrites", which have a high coercivity and are used to make ferrite magnets. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. The most common soft ferrites a Manganese-zinc ferrite (MnZn, with the formula MnaZn(1-a)Fe2O4). MnZn have higher permeability and saturation levels than NiZn. Nickel-zinc ferrite (NiZn, with the formula NiaZn(1-a)Fe2O4). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1 MHz. " Ferrites DO have iron in them. Look at the formulae you posted. The Manganeze Zinc Ferrites have Fe204, as do the Nickel Zinc Ferrites. In effect they are a ceramic iron alloy |
#4
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
harry wrote:
On Mar 2, 7:14 am, micky wrote: More about magnetism and MRI's It came up here wrt my planned MRI that there seemed to be things not made out of iron that were subject to magnets. By coincidence I came across this. From Wikip ...http://en.wikipedia.org/wiki/Ferrite_core Ferrites Ferrites are ceramic compounds of the transition metals with oxygen, which are ferromagnetic but nonconductive. Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. So I guess all these compounds and maybe more (that aren't used commericialy or not in transformers) would be magnetic like iron, but not containing iron, and to top it off, nonconductive. What a complicated world we live in, where there are general rules and exceptions to the rules. Nowadays, people are most likely to see ferrite cores as the small cylinders near the end of electric wires, such as USB cables, power supply adapter cables, etc. "hey have a low coercivity and are called "soft ferrites" to distinguish them from "hard ferrites", which have a high coercivity and are used to make ferrite magnets. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. The most common soft ferrites a Manganese-zinc ferrite (MnZn, with the formula MnaZn(1-a)Fe2O4). MnZn have higher permeability and saturation levels than NiZn. Nickel-zinc ferrite (NiZn, with the formula NiaZn(1-a)Fe2O4). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1 MHz. " Magnetic fields are also associated with any electric current. Such as those coils in the MRI. Greg |
#5
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
micky wrote:
More about magnetism and MRI's It came up here wrt my planned MRI that there seemed to be things not made out of iron that were subject to magnets. By coincidence I came across this. From Wikip ... http://en.wikipedia.org/wiki/Ferrite_core Ferrites Ferrites are ceramic compounds of the transition metals with oxygen, which are ferromagnetic but nonconductive. Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. So I guess all these compounds and maybe more (that aren't used commericialy or not in transformers) would be magnetic like iron, but not containing iron, and to top it off, nonconductive. What a complicated world we live in, where there are general rules and exceptions to the rules. Nowadays, people are most likely to see ferrite cores as the small cylinders near the end of electric wires, such as USB cables, power supply adapter cables, etc. "hey have a low coercivity and are called "soft ferrites" to distinguish them from "hard ferrites", which have a high coercivity and are used to make ferrite magnets. The low coercivity means the material's magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material's high resistivity prevents eddy currents in the core, another source of energy loss. The most common soft ferrites a Manganese-zinc ferrite (MnZn, with the formula MnaZn(1-a)Fe2O4). MnZn have higher permeability and saturation levels than NiZn. Nickel-zinc ferrite (NiZn, with the formula NiaZn(1-a)Fe2O4). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies above 1 MHz. " Even iron transformer plates, are plates glued together to avoid conduction. Greg. |
#6
|
|||
|
|||
Quote:
I understand the character "a" to be a variable, but the formula doesn't make sense. If you presume "a" is any number above one, the term (1-a) becomes a negative number, suggesting you have fewer than zero zinc atoms in the ferrite. If you presume "a" is one, the term (1-a) becomes zero, and you have no zinc atoms in the ferrite at all. It therefore consists entirely of manganese and rust OR nickel and rust. And, if "a" is any number less than one, you have zero, or fewer than zero manganese or nickel atoms in your ferrite. I'm certainly not a chemist, but that "a" character needs some explanation. |
#7
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
On 3/3/2013 8:37 AM, Kurt Ullman wrote:
In article , micky wrote: Just for the record, I was told the MRI machines were magnetic even when they are off.. That's why I think they won't let me in the room just to look at a machine with no one in it, until I've undressed. They let me look at it through a window. Yep. That is because it is never off, it is just in standby. From my MRI safety lectures in the past, IIRC, to turn it all the way off there is an emergency "quenching" that stops the superconducting magnets from conducting but it take a while, and a whole bunch of money, to bring it back online. The "whole bunch of money" is because the emergency shutdown procedure vents the liquid helium coolant outside. |
#8
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
On Sun, 03 Mar 2013 10:06:58 -0500, George
wrote: On 3/3/2013 8:37 AM, Kurt Ullman wrote: In article , micky wrote: Just for the record, I was told the MRI machines were magnetic even when they are off.. That's why I think they won't let me in the room just to look at a machine with no one in it, until I've undressed. They let me look at it through a window. Yep. That is because it is never off, it is just in standby. From my MRI safety lectures in the past, IIRC, to turn it all the way off there is an emergency "quenching" that stops the superconducting magnets from conducting but it take a while, and a whole bunch of money, to bring it back online. The "whole bunch of money" is because the emergency shutdown procedure vents the liquid helium coolant outside. http://www.youtube.com/watch?v=5z33ZcDgavY ...and a bunch more. |
#9
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
On Sun, 03 Mar 2013 08:37:20 -0500, Kurt Ullman
wrote: In article , micky wrote: Just for the record, I was told the MRI machines were magnetic even when they are off.. That's why I think they won't let me in the room just to look at a machine with no one in it, until I've undressed. They let me look at it through a window. Yep. That is because it is never off, it is just in standby. From my MRI safety lectures in the past, IIRC, to turn it all the way off there is an emergency "quenching" that stops the superconducting magnets from conducting but it take a while, and a whole bunch of money, to bring it back online. Thanks. Someone at the MRI office said they were permanent magnets, but I suspect she was just guessing. Probably never had to do the emegency shutdown. |
#10
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
On Sun, 03 Mar 2013 16:45:22 -0500, micky
wrote: On Sun, 03 Mar 2013 08:37:20 -0500, Kurt Ullman wrote: In article , micky wrote: Just for the record, I was told the MRI machines were magnetic even when they are off.. That's why I think they won't let me in the room just to look at a machine with no one in it, until I've undressed. They let me look at it through a window. Yep. That is because it is never off, it is just in standby. From my MRI safety lectures in the past, IIRC, to turn it all the way off there is an emergency "quenching" that stops the superconducting magnets from conducting but it take a while, and a whole bunch of money, to bring it back online. Thanks. Someone at the MRI office said they were permanent magnets, but I suspect she was just guessing. Probably never had to do the emegency shutdown. Well, they are "permanent" in that they don't use energy when they're sitting there. They sure suck it down ramping up and then, of course, have to shed it on shut-down. |
#11
|
|||
|
|||
Mickey:
Why don't you just tell the people at the hospital where you're going to have your MRI done about your concerns. They may be able to give you some idea of how to test to see if the MRI's magnetic field will affect you BEFORE they sit you onto the table and slide you into the machine. |
#12
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
On Mon, 4 Mar 2013 17:53:10 +0000, nestork
wrote: Mickey: Why don't you just tell the people at the hospital where you're going to have your MRI done about your concerns. I did. Although it was an "Imaging Clinic", not a hospital. The front desk at the orthopedist had detailed flyers for each of two chains of such clinics here. . They may be able to give you some idea of how to test to see if the MRI's magnetic field will affect you BEFORE they sit you onto the table and slide you into the machine. You don't have to raise the subject. They do. There's a questionnaire about whether you've ever worked with metal, and around 30 questions about what metal things you have in your body. There are loads of things that surgeons lieave in people's bodies, on purpose. Pins in their bones, staples, stents, blood vessel clips, even things in people's heads. I'd heard of many of them, but not all. But I don't have any of that, and the only question was, metal filings in my eye. Both places asked the same question, and they were both vague, imo. When I said I was just a hobbyist, maybe 3 hours of grinding total in the last 30 years, the first place said, Don't worry. It's for people who work with a grinder or sheers or a saw for a living, 40 hours a week. Couldn't take it at the first place because of claustrophobia. The second place had a machine with a larger bore (but still closed. Doctor insisted on closed, not open, because the image is much better) And the moment I started to ask the same question to the woman on the phone at the second place, she interrupted and said, You need an orbital X-ray. The x-ray machine didn't move, so I don't know what orbit they're talking about, but I think it's my eyeballs themselves Yes, that's it. http://en.wikipedia.org/wiki/Orbital_x-ray http://en.wikipedia.org/wiki/Orbit_%28anatomy%29 The orbits are the cavities in the skull where the eyes are found, and maybe they are also the eyes. . My eyes don't have any metal in them, andt it was worth one x-ray to find out. And I'll pay closer attention from now on so I won't need another x-ray. The second clinic depended on earplugs, which the tech said did a better job of keeping the noise I heard down, and yet I could still har him. Not good enough, and I frieaked out in about 5 minutes. I thought all these places had headphones with music and even maybe radio stations. I should have asked about that. |
#13
Posted to alt.home.repair
|
|||
|
|||
More about magnetism and MRI's
On 03-02-2013 02:14, micky wrote:
What a complicated world we live in, where there are general rules and exceptions to the rules. Look up the words: ferromagnetic Paramagnetic Diamagnetic -- Wes Groleau To compel a man to furnish contributions of money for the propagation of opinions which he disbelieves and abhors, is sinful and tyrannical. Thomas Jefferson |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Magnetism is really -- WHAT?? | Electronics Repair | |||
Metal in the Eye and MRI's | Metalworking | |||
A valuable lesson on magnetism | Metalworking | |||
Sony CRT Magnetism SCC-L04MM-A IBM P202/6558-43N | Electronics Repair |