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Author Topic: How can moving metal cause magnetism?  (Read 1416 times)

Offline Atomic-S

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How can moving metal cause magnetism?
« on: 22/03/2015 05:24:42 »
According to
, the spinning molten metal inside the earth is responsible for its magnetic field. The phenomenon has been demonstrated in the laboratory.  That is puzzling. Although it has long been known that moving charged objects will generate a magnetic field. I find it unclear how simply moving molten metal would.  It would seem that the phenomenon would be impossible unless the moving metal somehow involved unbalanced charges.  But how does that take place? This is the first time I ever heard it implied that melting metal will create unbalanced charges or electrical currents within it. What is the mechanism?  Also, if this is so, will a nonmoving pot of melted metal create such fields, and what if the pot moves in one direction irrotationally with respect to the observer? And will a spinning nonmetallic conductive medium such as salt water generate a magnetic field?


 

Online evan_au

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Re: How can moving metal cause magnetism?
« Reply #1 on: 22/03/2015 06:36:46 »
Quote
the phenomenon would be impossible unless the moving metal somehow involved unbalanced charges
The laboratory tests with molten sodium required a small "seed" magnetic field. This would induce currents in the moving sodium, which then generate a larger magnetic field.

Because the motion of the sodium is chaotic, the magnetic field is also chaotic, exhibiting random reversals (like the Earth).

In the case of the Earth, this seed magnetic field could come from crystallised iron in the core.

Quote
And will a spinning nonmetallic conductive medium such as salt water generate a magnetic field?
A salty ocean on Ganymede did affect the magnetic aurora from Jupiter's magnetic field.

However, the resistivity of salt water is far higher than the resistivity of metals, so any magnetism-induced currents would dissipate much more quickly in salt water than in a liquid metal.
 

Offline yor_on

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Re: How can moving metal cause magnetism?
« Reply #2 on: 23/03/2015 22:13:24 »
very cool, would you happen to have a link to the laboratory tests too, Evan?
 

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Re: How can moving metal cause magnetism?
« Reply #2 on: 23/03/2015 22:13:24 »

 

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