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Registered Member #61406
Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268
Was wondering if you have a copper tube with current going right to left and a magnetic field going right to left on the same axis, would a voltage difference occur between the inside and outside of the copper tube. Cheers
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Hall voltage is developed with the magnetic field normal to the current. So if the current and the field share the same axis, then no, no Hall voltage will be generated.
Registered Member #61406
Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268
Thanks,say you have a plastic pipe in a coil like a solenoid and you pump salt water through it,will it charge up like a inductor,would a couple meters a sec water flow be compared to a couple amps?
Registered Member #61406
Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268
Second question? Some information says a moving conducive fluid does,but does it need something external, seating on the fence, if I could find my compass I could test it,but then question like drift velocity in copper compared to meters a second in a fluid, don't know if I can expand two character, maybe others could offer there question relating to that question.
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556
moving a conductive fluid will have as little effect as moving a conductive wire; if no (alternating) current is flowing, there will be no (alternating) magnetic field generated, and therefore no current flow in the outer coil. putting AC on the outer coil may induce currents in the conductive fluid, but as the whole fluid is conductive, the currents will flow internally, and the interaction with the outer magnetic field will produce no net fluid movement.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
If you want to see the Hall effect generate tangible powers and voltages, search for MHD (MagnetoHydroDynamic) generators, and Hall. Here the velocities are large, the current carrier density is low, and as they are trying to make generators, the field is high.
Registered Member #61406
Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268
This thing is a cross between a battery and transformer, would the ac magnetic field increase the cell voltage of the battery and the plates supply the charges.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Vaguely recall reading that someone had made one using a monster neo magnet (the flesh-crushing sort) and it worked very well. Alas not efficient at all even in salt water compared to a superconducting magnet but enough to get an honourable mention at science fair.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Just remember, MHD pumping of seawater (or liquid sodium, in real nuclear reactor plants) has nothing to do with the Hall effect. It's plain old force on current-carrying conductors in a transverse magnetic field.
Here is one distinguishing feature of the Hall effect, which is typically very small in magnitude: The sign of the voltage tells whether the moving charge carriers are positive or negative.
Hall worked in the late 19th century, before the discovery of electrons (much less the electron theory of charge conduction in metals). But after electric motors and three-phase AC power distribution were well established.
Hall's voltage measurements, on thin metal films with huge current densities, indicated that most of the current was being handled by something with a negative charge, moving counter to the electric current direction. Something that wasn't moving very fast, so it must have a very large charge density (many coulombs per cubic mm). Today we refer to the drift velocity of electrons.
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