Weed_O_Whirler t1_je6a94c wrote on March 29, 2023 at 6:40 PM

Reply to comment by TitleFlimsy in Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science by AutoModerator

Oh yeah, a magnet like that would kill you in so many ways, so fast. Of course it would rip the iron out of your blood, but that's child's play in the ways you'd died. Your neurons would become polarized and unable to fire. The cells in your body would all magnetize, ceasing any and all functions. You're toast.

mfb- t1_je7r7om wrote on March 30, 2023 at 12:46 AM

A neodymium magnet won't produce a field stronger than 1-2 T. We have MRI machines that are significantly stronger than that, and they don't kill their patients.

Weed_O_Whirler t1_je8e4g9 wrote on March 30, 2023 at 3:51 AM

So I'm honestly curious - is 1-2 T the theoretical max for how strong a neodymium magnet can be? Or is there an easy, back of the envelope, way of calculating it? I tried to scale up a small one to the mass of the Earth, but couldn't find any easy way of doing it, but my estimate made it quite large.

mfb- t1_je8wf3w wrote on March 30, 2023 at 7:25 AM

Permanent magnets have a saturation magnetization. Trying to apply stronger fields doesn't magnetize the material more, and if you drop the external field then the field of the magnet decreases, too. In practice you get around 1.3 T for neodymium magnets, theoretical values might be slightly higher. This publication calculates 1.32 to 1.38 T.

The size of the magnet doesn't matter, you just scale up everything linearly in space and the field gets larger but not stronger.