I remember reading that an MRI’s magnetic field is more powerful than the earth’s, so shouldn’t my compas’ needle be more attracted by MRIs rather than the magnetic north, and therefore point towards it?
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The magnetic field of the mri doesn’t travel far enough to effect your compass.
If you were close to one with a compass something would defintely happen, I dunno what though..
Imagine a candy store the size of big mall thats Earth and there is a small cart full of candy. Now if a bunch of kids were near the cart and the mall was far away, then yah they would go towards the cart, however any where 50 ft away all the kids will see that big mall size candy shop and gravitate there.
Not so ELI5: magnetism obeys Coulomb’s Law which is inversely proportional to the distance squared (i.e. it obeys an inverse square law with distance) that basically means distance will depreciate the force by the distance square.
BACK to eli5, these kids have bad eye sight for every feet the kids walk away the image would shrink faster then their distance. For example if they walk 2 feet the image shrinks by 4x, 4 feet 16x and so on.
The intensity of the magnetic field dissipates quickly the further away you are from it. It’s identical to how from up close, a candle is brighter than a far away bright light or the brightest star in the sky.
If you are close enough to an MRI it will affect the compass. Compared to the earth’s magnetic field, the MRI is so extraordinarily weak that you don’t have to travel far from the machine for the earth’s magnetic field to be orders of magnitude stronger than the magnetic field from the machine.
You might then ask where on earth can you go to experience a magnetic field as strong as an MRI? You certainly won’t experience that on the surface. If you dig a hole towards the center of the earth the magnetic field will increase in intensity and at some depth it will be stronger than standing right next to an MRI.
a larger magnet has a larger magnetic field
eg the distance between the Earth’s north pole and south pole is a lot larger than the distance between the MRI’s north and south pole
the MRI is only stronger because it’s trying to influence a smaller area than the Earth, it’s more concentrated but not a more powerful magnet
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