Magnetic spin and a magnetic field

AI Thread Summary
When a nucleus is placed in a magnetic field, its spin orientation affects its energy state, with spins aligned with the field (spin up) being lower in energy than those against it (spin down). The confusion arises from the analogy of small magnets, where opposite poles attract, suggesting a lower energy state. However, in nuclear magnetic resonance (NMR), the energy difference is due to the interaction of the nuclear spins with the external magnetic field, not merely attraction. The alignment of spins with the magnetic field represents a more stable configuration, thus a lower energy state. Understanding this concept is crucial for grasping the principles of NMR.
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So I'm starting to read about NMR and I have a very simple question. When we subject a nuclei to a magnetic field, we always draw the spins going with the magnetic field as having lower energy than those going against. If I was to take a huge bar magnet as a field and then took little magnets next to it, opposites will attract. Isn't this the lower energy? So why is it that the lower energy state is the one going with the external field?

Any insight would be greatly appreciated!
 
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depends whether its spin up or spin down
 

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