Xtracting energy out of a magnet

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The discussion centers around the concept of energy dynamics in ferromagnetism, specifically addressing the claim that energy is required for an iron object to become ferromagnetic when exposed to a magnetic field. It is clarified that when a ferromagnetic object enters a magnetic field, it actually transitions to a lower energy state where all magnetic spins align, thus releasing energy rather than consuming it. The conversation highlights the role of temperature in affecting magnetic states, with higher temperatures disrupting the alignment of spins and leading to a paramagnetic state. The Einstein de Haas effect is introduced as a phenomenon where the alignment of spins in a ferromagnet under an external magnetic field results in a change in angular momentum, observable as rotation of the magnet. It is emphasized that energy must be supplied to reverse the process, debunking the notion of extracting infinite energy from magnetic fields.
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In a dutch forum I'm in discussion with a crackpot about extracting energy out of a magnet. He claims that when a iron object enter the range of a permanent magnet it need energie to become ferromagnetic. Is this really so and if it is where comes the energy from?
 
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A thing becomes ferromagnetic because that is the lowest energy state under the given conditions. If the paramagnetic state had a lower energy than the ferromagnetic state, then your object would not turn into a ferromagnet spontaneously.

Your "friend" is wrong.
 
So if i understand it correct: When a ferromagnetic object comes in a magnetic field, the lowest energy state is the stat where all magnetic spins point out the same direction. So you don't need energy, in fact the object gives energie away. So where do tehe energy go to?

Your "friend" is wrong.

Do you know crackpot's who aren't :smile:
 
Peter,

Ferromagnetism is the phenomenon where one atom tells its neigbor to align its spin along the same direction. This is an interaction that becomes dominant under a certain transition temperature. So a specimen will be (like gokul said) in its ferromagnetic state (if it has that specific property) rather then in the paramagnetic state. When you rise temperature, this spin spin-interaction will be disturbed and chaos will rise among the spins. Eventually with high enough temperature, all spins will be directed randomly : ie the paramagnetic state.

regards
marlon
 
Peterdevis said:
So where do tehe energy go to?

Good question. Ever heard of the Einstein de Haas effect ?

If you have a ferromagnet and you apply an external B field to align the spins, they will add up to produce a change in angular momentum (you know : J = L+S where S is the spin and L is the angular momentum, L is the TOTAL angular momentum), manifested by the rotation of the magnet. S changes due to the transition from paramagnetic to ferromagnetic (all spins align). But J must be constant and therefore L must change and this means that the specimen will rotate. You can actually observe this rotation.

The experiment is conducted by haning some ferromagnetic specimen (that is initially in its paramagnetic state, if you will) on a small string and then applying the external magnetic field B.

regards
marlon
 
another thing.. you don't want to think that if you put a ferromagnet in a field in one direction, you get some energy, so that if you take it out and put it in a field in the opposite direction, you get some more energy, rinse and repeat for infinite energy. In order to take the magnet out of the field, you have to add energy to it equal to the amount of energy gained by putting it in the field.
 
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