Classical Hall effect when current has neutral charge

In summary, when a current of both negative and positive charges is present along an infinite wire with a homogeneous magnetic field, a Lorentz force is exerted on both types of charges in the same direction. However, due to the opposite movements, the overall charge cancels out but there is still a current present. This can be observed in the classical Hall effect, where the opposite sign of the Hall coefficient for electrons and holes indicates that it is more appropriate to think of the current as positive "holes" moving rather than negative electrons. This confusion is resolved by modern quantum mechanical theory of transport in solids.
  • #1
Joker93
504
36
If i have a current of both negative and positive charges(i know that there is also current from only negative and only positive charges,i'm not confused) along an infinite wire of square cross-section,and the we put a homogeneous magnetic field normal to the current,then a Lorentz force acts on both the positive and negative charges and it is in the same direction for both of them(negative charges move in the opposite direction of the positive charges so from the equation of the Lorentz force,the negative sign from the negative charge and the negative sign from the velocity vector cancel each other out-considering positive velocity vector in the direction that the positive charges are moving).But because the forces act in the same direction AND because negative and positive charges attract each other,then we will have accumulation of both negative AND positive charges on near the one end of the wire.So,the question is,will there be a potential difference transverse of the wire like the normal classical Hall effect?
 
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  • #2
Adam Landos said:
If i have a current of both negative and positive charges
Then they will cancel and you will have no current.
 
  • #3
no,this is not the case.the overall charge will be zero but there will be current.one in one direction and one in another(check it out in books)
 
  • #4
You're assuming the wire to have an infinite length so how can the wire have ends?
 
  • #5
seems to me
one amp of 'Technician's current' , negative charge moving left to right
plus
one amp of 'Engineer's current' , positive charge moving right to left
adds to
two amps of either observer's current moving in whichever direction they believe current to flow.

Did i mis-read the question ?
 
  • #6
The negative “electron” current flows one way, while the positive “hole” current flows the other way.
That is really only one classical “current”, but what is it's magnitude and polarity. {-2, -1, 0, 1 or 2} ?

See; http://en.wikipedia.org/wiki/Hall_effect#Theory My bold.
Wikipedia said:
In the classical view, there are only electrons moving in the same average direction both in the case of electron or hole conductivity. This cannot explain the opposite sign of the Hall effect observed. The difference is that electrons in the upper bound of the valence band have opposite group velocity and wave vector direction when moving, which can be effectively treated as if positively charged particles (holes) moved in the opposite direction to that of the electrons.
Wikipedia said:
One very important feature of the Hall effect is that it differentiates between positive charges moving in one direction and negative charges moving in the opposite. The Hall effect offered the first real proof that electric currents in metals are carried by moving electrons, not by protons. The Hall effect also showed that in some substances (especially p-type semiconductors), it is more appropriate to think of the current as positive "holes" moving rather than negative electrons. A common source of confusion with the Hall Effect is that holes moving to the left are really electrons moving to the right, so one expects the same sign of the Hall coefficient for both electrons and holes. This confusion, however, can only be resolved by modern quantum mechanical theory of transport in solids.[4]
 

Related to Classical Hall effect when current has neutral charge

1. What is the Classical Hall effect?

The Classical Hall effect is a phenomenon in which a magnetic field applied perpendicular to an electric current in a conductor results in a voltage difference across the sides of the conductor. This effect is due to the Lorentz force, which causes the electrons in the current to be deflected, creating an imbalance of charges on opposite sides of the conductor.

2. How does the Classical Hall effect differ from the Anomalous Hall effect?

The Classical Hall effect occurs in conductors with a neutral charge, whereas the Anomalous Hall effect occurs in conductors with a non-zero net charge. Additionally, the Classical Hall effect is a linear relationship between the applied magnetic field and the resulting voltage, while the Anomalous Hall effect has a more complex relationship.

3. What is the significance of the Classical Hall effect?

The Classical Hall effect is significant in the study of materials and their properties, as it allows us to measure the charge carrier density and mobility. It is also used in various electronic devices, such as Hall sensors, which can detect magnetic fields.

4. How is the Classical Hall effect experimentally observed?

The Classical Hall effect is typically observed by applying a magnetic field perpendicular to a current-carrying conductor and measuring the resulting voltage across the sides of the conductor. The magnitude of the voltage is directly proportional to the strength of the magnetic field and the current, and inversely proportional to the thickness of the conductor.

5. Can the Classical Hall effect be used to determine the sign of the charge carriers in a material?

Yes, the direction of the voltage across the conductor can indicate the sign of the charge carriers. If the voltage is positive, it means that the charge carriers are positively charged, and if the voltage is negative, the charge carriers are negatively charged.

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