Talk:Hall effect

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Help with this template Comments: edit – history – watch – refresh When I take the yellow image below, and rotate it clockwise 90 degrees, it appears to resemble image "D" above. Except that the Hall voltage polarity is oppposite that of image "D".

Hi fellow wikipedians! I've just uploaded a large, detailed illustration of the Hall effect to Commons - see Image:Hall_effect.png -- Peo from danish Wikipedia

Nice!!--Krackpipe 18:07, 10 May 2005 (UTC)

• Great diagrams! 17:33, 27 February 2006 (UTC)

The diagram is great! excellent addition to the article Kupojsin 11:59, 2 February 2007 (UTC)

Contents 1 Schematic symbol 2 Diagram ownership 3 Important question 4 Hall coefficient 5 Symmetry 6 Hall Resistance 7 Differences in images 8 Materials 9 Advantages 10 Missing application 11 Typical values of the Hall coefficient? 12 Important question

[edit] Schematic symbol

What is the symbol for a Hall effect sensor (3 wire type) for use in a schematic diagram ? - Joshua Hrouda, 26/7/05

A full range of Hall Effect related articles at: http://www.bbautomacao.com/Sensors.htm

[edit] Diagram ownership

Some of the diagrams on the site belong to a company (Raztec). Something should probably be done about this.

[edit] Important question

How does the Hall voltage build up if only one type of charge accumulates at one side of the conductor? For example, electric current is the flow of electrons so they deviate from their 'normal' path and 'rush' to one side of the conductor. But where does the positive charge to accumulate at the opposite side of the conductor come from? RokasT 11:32, 30 December 2006 (UTC)

All solid materials are made from neutral atoms locked together in a crystal lattice. A conductor is conductive because some of the electrons are free to move away from their 'parent' atoms and wander throughout the lattice. The electrons have a negative charge, so they leave behind positive ions that cannot move. Whenever electrons are forced to gather together in one region (against their mutually replusive instincts) concentrations of 'naked' positive charges must be left exposed in others. Hence the negative voltage on one side of a Hall probe is exactly matched by a positive voltage on the opposite face. The only difference is that the electrons are drifting along the face as a current, while the positve ions are stationary. StuFifeScotland 14:42, 1 April 2007 (UTC)

Thanks for your explanation. ;-) RokasT 20:54, 1 April 2007 (UTC)

One more question: If holes moving in say the +y direction are viewed as actually electrons moving in the -y direction, the polarity of the hall voltage generated is the opposite! Especially since electrons exist physically whereas holes only represent absence of electrons. This means n and p semiconductors should show identical polarity in the hall effect experiment, which is not so as demonstrated by experiment. What explains this? Thanks. -AK 220.225.214.2 (talk) 10:20, 24 January 2008 (UTC)

[edit] Hall coefficient

Why isn't the Hall coefficient mentioned? R_H = 1/ne --82.43.144.131 18:01, 25 January 2007 (UTC)

[edit] Symmetry

This question is relevant to many articles in electromagnetism but here is as a good a place as any to bring it up: doesn't the Hall effect have to obey symmetry? E.g. if I reflect (in some horizontal axis) the system from that nice picture in the article, shouldn't the reflection also have the negative charge at the top of the Hall element? According to the theory, no (see parts B and C from that image). I know that the Right-Hand-Rule and vector cross-product come into this but these don't seem to be adequate explanations. I say this not to claim that all the physicists in the world are wrong and I'm right (I would far sooner take their word than mine!) but to ask whether it might be better explained (not necessarily in this article). There must at least some others who get confused about this point.--Ejrh 10:39, 15 April 2007 (UTC)

Good question. The reason is that the Magnetic field (being a pseudo vector) breaks the reflection symmetry you mentioned. Here's how it works:

Electric field and current are vectors, so they transform as you would expect under inversion/reflection. Magnetic field are pseudo vectors, so they don't change direction under inversion (which is taking every point mapping to . Magnetic fields are defined by , and you can check that it doesn't change to preserve that law. The flip that you mentioned is really an inversion followed by a 180 rotation, so basically, the magnetic field is now pointed downwards (from the rotation) from the reflection. Hence, the Hall effect doesn't break symmetry.74.102.181.37 06:37, 7 June 2007 (UTC)

Thanks very much! Your response lead me to Pseudovector which contains a nice example similar to this one. Ejrh 11:53, 1 July 2007 (UTC)

[edit] Hall Resistance

The Hall Resistance / Conductance is not defined in this article. I assume it's ratio of Hall (tranverse) voltage to current. It's important because the Quantum Hall effect does not reference to what is actually quantized.

I think the article "Hall Resistance" should be created.74.102.181.37 06:37, 7 June 2007 (UTC)

[edit] Differences in images

When I rotate the yellow image below, it apprears to match image "D" above, except the hall voltage polarity appears reversed. ````Harold````

[edit] Materials

It is mentioned that the magnitude of the effect is dependent on the type of material (as well as the thickness, current, etc.) I tried building one using a sheet of "1 ounce" copper on fiberglass. I was not able to observe any such effect. Is copper insensitive for this application? The commercial sensors seem to be made of silicon (for obvious reasons), but my understanding is that the material does not have to be a semiconductor. Plus, with a metal I can use much higher currents, which should result in a greater signal/noise ratio (sensitivity).

My point is: there should be information about the types of materials and their Hall output.

169.237.215.179 19:50, 20 August 2007 (UTC)

[edit] Advantages

Another advantage of hall devices is that they are devoid of the contact 'bounce' of mechanical switches. Switch bounce can cause confusion in digital circuits. I don't have a reference source on this, however. LorenzoB 17:45, 28 August 2007 (UTC)

[edit] Missing application

There should be some mention of the use of hall effect sensors for the detection of lid closure in consumer electronics devices. The Nintendo DS & DS Lite for example use the fixed magnet in the right speaker to trigger a hall effect sensor near the Y button. MacBooks use the magnets that hold the lid closed to trigger a sensor near the bottom-left corner of the keyboard. —Preceding unsigned comment added by 128.114.60.119 (talk) 21:28, 17 December 2007 (UTC)

[edit] Typical values of the Hall coefficient?

Why do we not list typical values of the Hall coefficient for various materials at room temperature? I've also had difficulty finding them online ... —Preceding unsigned comment added by Newagelink (talk • contribs) 04:46, 17 March 2008 (UTC)

[edit] Important question

It is written that hall effect shows why it makes sense to think of charge being carried by holes in semiconductors. How so? —Preceding unsigned comment added by Rainmanthe (talk • contribs) 15:19, 29 April 2008 (UTC)