Determining the direction and origin of the Hall current

In summary, a Hall current arises when electric currents transverse to a magnetic field exist. The Faraday current in this specific scenario is going upwards due to the magnetic field pointing into the page. The Hall effect creates a force pushing the electrons in the rightward direction, which in turn slows down the initial fluid flow. The external current links are necessary to balance the electric field created by the Hall effect and allow for the current to flow freely.
  • #1
TheCanadian
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A Hall current arises when electric currents transverse to a magnetic field exist. In this figure (found online), the Faraday current appears to be going upwards due to a magnetic field pointing into the page, but is this correct?

I'm largely just trying to understand the origin of the Hall current here: The Faraday current density, ##{\bf{J_F}} = \sigma \bf{v} \times \bf{B}##, is upwards since ##\bf{v}## is to the right and ##\bf{B}## into the page. (I realize the conductivity tensor is anisotropic due to the Hall effect, but I'm trying to understand how the Hall effect itself arises here.) Thus the force density from the Hall effect is ##\bf{F_H} = \bf{J_F} \times \bf{B}##, but this force associated to the Hall effect is pointing to the left and independent of charge, correct? It thus slows down the overall quasi neutral initial fluid flow. Thus why is a Hall effect current in the rightward direction created?

Also, perhaps this is a separate question but possibly related: why are the external current links (orange) in this configuration necessary? Why are they even connected in the first place for the generator? This appears to be a consequence of the Hall effect, but I'm unsure. Shouldn't only the electrodes connected by the light blue arrows be externally connected in a circuit since that's the direction of net current flow?

mhd_current.gif
 

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  • #2
The Hall current is created in the rightward direction due to the force from the Hall effect pushing the electrons in that direction. The external current links are necessary because the Hall effect also creates an electric field in the same direction as the current, which must be balanced or else the current will not flow. Thus, the external current links are necessary to complete the circuit and allow for the current to flow freely.
 

1. What is the Hall effect?

The Hall effect is a phenomenon in which a magnetic field applied perpendicular to a current-carrying conductor creates a voltage difference across the conductor.

2. How is the Hall effect used to determine the direction and origin of the Hall current?

By measuring the voltage difference created by the Hall effect and knowing the strength and direction of the applied magnetic field, the direction of the Hall current can be determined. The origin of the Hall current can be determined by analyzing the properties of the material and the applied magnetic field.

3. What is the formula for calculating the Hall current?

The formula for calculating the Hall current is IH = B * n * q * Vd, where B is the strength of the magnetic field, n is the charge carrier density, q is the charge of the carrier, and Vd is the drift velocity of the charge carriers.

4. Can the Hall effect be observed in all materials?

No, the Hall effect can only be observed in materials that have free charge carriers, such as metals, semiconductors, and some insulators.

5. How is the Hall effect used in practical applications?

The Hall effect is used in various practical applications, such as magnetic field sensors, current sensors, and in the study of electronic properties of materials. It is also used in the measurement of electrical conductivity, carrier concentration, and mobility in materials.

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