I would think this has something to do with the intrinsic quantumagnetic moment of the metal, but I'm curious if every metal would behave this way in liquid state , and if there are any practical applications of this .
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$\begingroup$ I didn’t know about this effect, but this Youtube video is a simple demonstration. $\endgroup$– rob ♦Commented Dec 28, 2022 at 5:05
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$\begingroup$ Do you have a reference to the effect you have in mind? The video I just linked has a radial electric current and a vertical magnetic field, so the fluid rotation is caused by the Lorentz force. $\endgroup$– rob ♦Commented Dec 28, 2022 at 5:07
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$\begingroup$ Yes that one .. $\endgroup$– GaugeCommented Dec 28, 2022 at 9:09
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1 Answer
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In this video demonstration, the mercury fills an annular channel between two ring-shaped electrodes:
(The powder is talc, which floats on the mercury and makes it easier to see the motion.) An electric current flows radially through the mercury metal from the inner electrode to the outer electrode.
When the ring-shaped magnet is placed in the center of the mercury, the mercury is subjected to a vertical magnetic field. The current experiences a Lorentz force,
$$ \vec F=q\left( \vec E +\vec v \times \vec B \right) $$
This force is perpendicular to the vertical $\vec B$ and to the radial current $q\vec v$, so the force points in the circumferential direction. That's what causes the flow. Without the electrodes, the mercury would not rotate. The video shows the rotation reversing when the magnet is flipped over, but reversing the direction of the current would reverse the flow as well.
