View source for Talk:Homopolar generator

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* <nowiki>[[Electrical generator#Dynamo|dynamos]]</nowiki> Anchor [[Electrical generator#Dynamo]] links to a specific web page: [[Dynamo]]. The anchor (#Dynamo) is no longer available because it was [[Special:Diff/624548379|deleted by a user]] before. <!-- {"title":"Dynamo","appear":{"revid":5118423,"parentid":4201450,"timestamp":"2004-06-21T12:56:21Z","removed_section_titles":[],"added_section_titles":["Developments","Faraday","Dynamo","Self-excited generator","Gramme dynamo","Concepts","See also"]},"disappear":{"revid":624548379,"parentid":624547944,"timestamp":"2014-09-07T15:25:56Z","replaced_anchors":{"Alternating current generator":"Alternating current generators"},"removed_section_titles":["Dynamo","Alternating current generator"],"added_section_titles":["Direct current generators","Alternating current generators"]}} -->
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== A crank is inserting links to his relativity denial website by hiding them as 'external references' ==

Self-promotion is against wiki policy, and since it seemed bad form to have two separate link sections I removed them.  <span style="font-size: smaller;" class="autosigned">— Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/85.80.170.103|85.80.170.103]] ([[User talk:85.80.170.103|talk]]) 01:22, 13 December 2013 (UTC)</span><!-- Template:Unsigned IP --> <!--Autosigned by SineBot

 <small class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/124.171.32.231|124.171.32.231]] ([[User talk:124.171.32.231|talk]]) 03:42, 22 December 2014 (UTC)</small><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

== Comments for the explanation table ==
I think the explanation table is somewhat misleading, when it terms, that it if both disk and indicator are moving the result is undetermined. It is surely not undetermined. Like some strange explanation also tries to say:
''The voltage is "undetermined" when both the indicator and the disk are rotated, regardless of whether the magnet is moving. There is an EMF and a nonuniform charge density, but no reaction of the indicator.[3] An electric field is generated, but no voltage is brought out for display. This differs from the different relative motions of the parts of a rectilinear homopolar generator (where the answer would be "No").''
I think this is explanation is unnecessarily complex. Simply stated: 
If the magnet rotates or not doesn't make any difference. If both indicator and disk rotate only the relative difference in rotation is relevant for the voltage seen on the indicator, which means if both rotate at the same speed the indicator doesn't see any voltage. The reason for this is simple, if both rotate at the same speed, then also the wires of the indicator circuit will develop the same voltage as the disk itself (the wire behaves the same as a second disk), therefore the indicator wouldn't see any voltage difference. Peace [[Special:Contributions/83.77.199.33|83.77.199.33]] ([[User talk:83.77.199.33|talk]]) 19:01, 15 February 2010 (UTC) 

== Current direction? ==
Nearly all cases of which wiki talks about electromagnets, could we add the direction of which the current flows? [[User:Seb-Gibbs|Seb-Gibbs]] ([[User talk:Seb-Gibbs|talk]]) 20:37, 12 July 2009 (UTC)

The generator is AC not DC  <small class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/216.229.79.241|216.229.79.241]] ([[User talk:216.229.79.241|talk]]) 22:33, 26 June 2015 (UTC)</small><!-- Template:Unsigned IP --> <!--Autosigned by SineBot-->

That is incorrect, it IS a DC offset potential !  <!-- Template:Unsigned IP --><small class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/47.182.228.198|47.182.228.198]] ([[User talk:47.182.228.198#top|talk]]) 11:18, 27 January 2019 (UTC)</small> <!--Autosigned by SineBot-->

== How it works ==
Paragraph from the bottom of the page:<br>
"The correct interpretation of the velocity of the electron is that it is relative to the static parts of the machine, which are the sliding contacts and the circuit to which they are connected. In the language of special relativity, these objects act as the 'observer'. It is the velocity of the electron relative to these components that causes it to experience the Lorentz force."<br>
How can this be true, since the results of moving the whole machine conflicts with this statement.  [[User:Seb-Gibbs|Seb-Gibbs]] ([[User talk:Seb-Gibbs|talk]]) 20:37, 12 July 2009 (UTC)

== Earliest Patent? ==
Is it certain that the earliest patent referenced (US238631) is really a homopolar generator? I'm certainly no expert, but it looks like an induction dynamo to me. See: [http://www.google.com/patents?id=fCxBAAAAEBAJ&dq=238631/ US238631 at Google Patents]
[[Special:Contributions/70.60.39.47|70.60.39.47]] ([[User talk:70.60.39.47|talk]]) 23:25, 30 June 2008 (UTC)

You're correct, it is not a homopolar generator. [[User:Tkircher|Tkircher]] ([[User talk:Tkircher|talk]]) 01:54, 23 February 2010 (UTC)

== Misguided: How magnetism makes current ==
Since Lorentz Force Law and not traditional induction is governing the generation of current in the Homopolar Generator isn't the section "How magnetism makes current" somewhat misplaced? --[[User:Enghoff|Enghoff]] 04:40, 14 September 2007 (UTC)

==bullshit==
Any reason we can't remove the bit about self-excited generators, aka perpetual motion machines, since we don't have a meaningful reference and aren't going to get one? Or should we link perpetual motion machines and bullshit to this page? Or is this some weird bit of gay humor? Here's a reference: http://news.yahoo.com/s/nm/20060817/sc_nm/technology_energy_dc_1

:No reason. I deleted them for you. However, I think that Wikipedia policy would allow factual references to real, if futile or fraudulent, attempts to create perpetual motion machines. For example, it's OK to say 'Company X is trying to market a perpetual motion machine based on the HPG', as long as we make it clear that it is a perpetual motion machine and therefore only a fairy story. --[[User:Heron|Heron]] 09:58, 19 August 2006 (UTC)

:Never say never. Perhaps there is something we do not understand about the universe and its physics. It is assumed that we are know everything and all of our theories are absolutely correct and complete. However, this may not be quite the case. For instance, no one it seems understands just what a magnetic feild is. We dont have a unified field theory. We dont really understand where any of this comes from (although some religious types have a claim to this). Some scientists perhaps do seem to see their science is a religion, and for who many things are simply a matter of faith. Some do not contemplate for a second that maybe some of our theories are workable in certian situations, but they may be insufficient in giving a truly complete and accurate picture of the universe and how it all works. Even though present theories might explain things with sufficiency for some applications does not mean they are totally complete. Scientists it seems are so trapped in the box they have been put in that they are unwilling to challenge, retest and revisit things, think beyond the theories already established, and be able to accept the possibility that some theories are not entirely complete if some evidence was found to show that all things are not as they seem. Many rely simply on faith that the current theories are complete and defend them religiously. I for one, hope that there is a way to have a perpetual motion machine. It is the only way this civilisation will be able to survive. What are we going to do when all of the oil runs out? Not only oil, but what happens when we run out of copper? It would also be better for the planet too, so we no longer have to use up all of her resources. I am not saying either that I have seen enough proof of free energy. But I am open minded about it. We barely understand anything at all, there is so much we dont know. If I went back 400 years and told people we could send pictures and sound through the air, they would have laughed and said thats impossible. People once thought people who thought the world was round were nuts. If no one ever questioned the status quo, we would have never known differently. Perhaps, one day we will laugh at the idea that once people thought perpetual motion was insane. 

[[User:Millueradfa|Millueradfa]] 13:58, 19 August 2006 (UTC)

::I've never heard of a scientist who 'assume[s] that we are know everything and all of our theories are absolutely correct and complete'. Anyway, that's not the point. Wikipedia is here to describe the world as it exists, not as some people dream that it might be in the future. By all means dream, and good luck to you, but please don't write it in Wikipedia until it is proven. --[[User:Heron|Heron]] 17:44, 19 August 2006 (UTC)

:::Because this device is not readily understood by beginning Physics students it lends itself to misunderstanding, and claims that it operates in some 'special' new way, thus feeding the free energy rumor mill. A paragraph about how it forms the core of several (purported) free energy/perpetual motion machines would not be amiss in alleviating some of this confusion. I bet half the people reading this article got here from a fringe alternative energy website.

:::I do get tired of people saying things don't work because they violate laws of physics instead of just saying that, "to date, no rigorous scientific testing has ever shown one of these machines to produce anti-gravity or over unity energy." Claiming no one has ever made a working device is a fact, claiming that it will not work because it violates a law of physics is a belief. Now if you will excuse, I'm going to go play with my [[Johann Bessler|Bessler Wheel]], and my [[SMOT]], which I will get working any day now. :P
{{User:UBX/wikiquotes_altscience_1}}<br style="clear:both;">
::::[[User:Tiki God|Tiki God]] 02:42, 14 September 2007 (UTC)

==research==
Umm...a compulsator is a specialized type of alternator. It is not either a Faraday disk nor a drum HPG. I have built  and used both.  I can also tell you that without relative motion between the armature and the field, you get no voltage in an HPG.  This article needs to researched more rigorously

:Your first point is correct, so I fixed the article.  Your second point is not correct.  Relative motion between the circuit and the field is irrelevant, since the field is uniform.  What counts is relative motion of the rotor and stator, within the uniform field.  --[[User:Heron|Heron]] 20:10, 14 September 2005 (UTC)

==Gaypolar==
Why is there still/again a [[Gaypolar generator]] page (even if it is a redirect)? --[[User:Art Carlson|Art Carlson]] 15:45, 13 January 2006 (UTC)

==Dubious material==
This is highly dubious "''. However, there are no records of the performance of [''Tesla's''] machine, nor of anybody else having tried to build one''". A citation is needed, or the sentence needs to be revised or removed. [[User:204.56.7.1|204.56.7.1]]

:: removed the above sentence, till a citation is provided. [[User:134.193.168.244|134.193.168.244]] 16:15, 7 April 2006 (UTC)

:::That was me, and I admit that I can't provide a citation, since it was just a statement of my own inability to find any evidence that one was ever built. I was hoping that someone would find an example of one and prove me wrong!  While we're on the subject, does anybody know what a "[[Forbes dynamo]]", mentioned in the article, is or was, please? --[[User:Heron|Heron]] 17:15, 7 April 2006 (UTC)

:::::: G. Forbes, "U.S. Patent 338169 Dynamo electric machine". That'[s his patent. [[User:134.193.168.244|134.193.168.244]] 17:40, 7 April 2006 (UTC)
:::::: I also just read from Valone's article that you can find info on the Forbes dynamo in an article in the Journal of the IEEE by Robert Belfield (Sept, 1976; pg., 344). [[User:134.193.168.244|134.193.168.244]] 17:52, 7 April 2006 (UTC)

:::Thanks. I must go and check those out. --[[User:Heron|Heron]] 19:39, 7 April 2006 (UTC)

==Move?==
Could someone make a [[List of homopolar generator patents]] and move the list there? [[User:204.56.7.1|204.56.7.1]] 19:40, 6 April 2006 (UTC)

==Referenced material==
The following was removed .... 
: ''The Faraday homopolar generator has been claimed to be a case of Sir [[William Thomson]]'s "''current accumulator''" and provide a basis for "''free energy''".((ref|telsa01))((ref|Kincheloe)) The current, once started, may be sufficient to maintain itself and even increase in strength and the device would be operated as a self-excited generator. Under certain conditions the process of obtaining the electrical output energy is not manifested as a accompanying load to the driving source. The back electromotive forces that occurs in this generator where there is relative motion between the armature of the motor and the external magnetic field in devices heretofore recognized by the scientific community prevent this, though. 

* note|telsa00 Nikola Tesla, "''[http://www.andrijar.com/teslahom/index.html Notes on a Unipolar Dynamo]''". The Electrical Engineer, N.Y., Sept. 2, 1891. (Also available at tesla.hu,  [http://www.tesla.hu/tesla/articles/18910902/index.htm Article 18910902])
* note|Kincheloe Robert Kincheloe, "''[http://www.rexresearch.com/kinchelo/kinche~1.htm Homopolar "Free-Energy" Generator Test]''". Society for Scientific Exploration; San Francisco, June 21, 1986. [Revised: February 1, 1987]

Heron 's coments @ Description and operation : ''rm free energy rubbish; Thomson's accumulator was a lead-acid battery, and the 'free energy' citation is from DePalma, who is wrong''

Depalma and others are '''wrong''' because of the ''back electromotive forces'' that is not accounted for or misrecorded. The citation is not from Depalma, but  Robert Kincheloe [Professor of Electrical Engineering (Emeritus), Stanford University]. As to Thomson's "accumulator", it was not his "battery" but part of his reaserch into magnetodynamic generators. [[User:134.193.168.236|134.193.168.236]] 20:59, 7 April 2006 (UTC)

:Thank you, '236.  I hope you weren't offended by my "rubbish" comment.  I was criticising the sources that you were citing, not your own words.  It seemed to me that the source of the "not manifested as a load" statement was De Palma, as paraphrased by Kincheloe, but perhaps I misunderstood.  This is where Kincheloe says:
::''The term "free-energy" refers to the claim by DePalma [1] (and others [2]) that it was capable of producing electrical output power that was not reflected as a mechanical load to the driving mechanism but derived from presumed latent spatial energy. ''
:As for Thomson, the only substantial record of an accumulator that I can find is of the Faure accumulator, which was a battery of some kind. The term "current accumulator" appears only in a passing comment by Tesla, with no explanation. I need to find out more about this.
:--[[User:Heron|Heron]] 21:49, 7 April 2006 (UTC)

== Other Names for Homopolar Generator ==

Other names for HPG.

* Faraday disk
* HPG

Should they be added and if so where? [[User:DeleteThis|DeleteThis]] 02:59, 23 May 2006 (UTC)


=== Added redirect from acyclic generator to here ===

Since the page did not exist, but unipolar generator and disk dynamo I added Acyclic Genertor and redirected it to this page. [[User:DeleteThis|DeleteThis]] 02:58, 23 May 2006 (UTC)

== Definitions of Alternators and Dynamos ==

From Dictionary.com

Alternator - An electric generator that produces alternating current. 

Dynamo - A generator, especially one for producing direct current.

[[User:DeleteThis|DeleteThis]] 02:59, 23 May 2006 (UTC)

== Structure of article ==

Current structure of article...


1 History and development <br>
2 Description and operation <br>
2.1 How magnetism makes current <br>
2.2 Disk type generator <br>
2.3 Drum type generator <br>
3 Physics <br>
4 See also <br>
5 References and further reading <br>
6 External links and other articles <br>

Does this make sense.

How would the other pieces be added into this one.

[[User:DeleteThis|DeleteThis]] 11:09, 26 May 2006 (UTC)

Any reference to how Sir Oliphant designed the 500MJ homopolar generator? and any data on its efficiency 1%? 10%? We need to show why it is worse for homopolar generators than alternators.

: 500MJ is around 140 kWh and that would translate to about 187hp/hr. One gallon of Gasoline contains ~121 MJ. This is around 4 gallons of gas. [[User:DeleteThis|DeleteThis]] 04:49, 28 May 2006 (UTC)


* Low speed flywheels, with typical operating speeds up to 6000 rev/min, have steel rotors and conventional bearings. For example, a flywheel system with steel rotor developed in a collaborative project at CCLRC in the 1980’s had energy storage capacity 2.3 kWh @ 5000 rev/min, and rated power 45kW. (rotor specific energy 5 Wh/kg, specific power 100 W/kg). [[www.itpower.co.uk/investire/pdfs/flywheelrep.pdf|ref]]
[[User:DeleteThis|DeleteThis]] 04:54, 28 May 2006 (UTC)

== Indicator? ==

Am I correct to assume that the term "indicator" in the table is a meter used to measure the voltage generated across the disk?  This is not 100% clear to me.  --[[User:Jakohn|Jakohn]] 21:08, 15 June 2006 (UTC)

I agree, the term "indicator" needs to be explained. I can't believe that moving the meter/sink would generate any current so anyone who understands what is meant by "indicator" kindly elaborate.  --[[User:Enghoff]] 09:58, 14 September 2007 (IST)

== Trying to understand this ==

I apologise if these questions seem absurd, but I am a layperson trying to understand this.

I am trying to understand the homopolar generator, to visualise it. I think it consists of an axis, with a metal disk and a magnet attached to it? Does both the magnet and the disk rotate together, or just the one and the other remain stationary? I think I heard the magnet can either be stationary or move with the metal disk. However, strangely, if the magnet is moving but the metal disk is stationary you will get no voltage. I also guess the leads, which could connect to say a lightbulb, one lead would connect to the centre of the metal disk, and another to its edge? I think since the disk rotated, metal brushes are used to connect the wire to the moving piece. And what about this homopolar field. I thought magnets always had two polarities. How can a magnetic field have the same polarity everywhere? 

[[User:Millueradfa|Millueradfa]] 13:19, 19 August 2006 (UTC)

:Your question is quite reasonable, given that the article doesn't have a clear diagram. The disc rotates like a wheel on an axle. As you said, there are brushes to make the connections. The magnet is roughly C-shaped and is placed with the north pole on one side of the disc and the south pole on the other, so that the magnetic field lines are perpendicular to the disc and pass through it. Ideally, each pole covers the entire surface of the disc. 'Homopolar field' means that the magnetic field is uniform over the disc's area. There are of course two magnetic poles, one on each side of the disc. --[[User:Heron|Heron]] 13:34, 19 August 2006 (UTC)

: Thank you for your response, it helped me understand it better quite a bit. 

: I do have another question. Does anyone know what would happen if the direction in which the device is spinning where to be reversed every so often? Perhaps, for instance, if the direction could be reversed every 90 degrees, or every 360 degrees, a permenant wire connection could be made to the device, with flexible pieces of wire. What would be the effects of this?

[[User:Millueradfa|Millueradfa]] 17:59, 23 August 2006 (UTC)

== megajoules? ==

"It produced 500 megajoules"

: What, over the course of its lifetime?  More context needed. — [[User:Omegatron|Omegatron]] 19:29, 25 November 2006 (UTC)

I agree. Media reporters and even amateur science people keep confusing POWER with ENERGY, eg: Kilowatts and Kilowatt Hours. (A joule is a watt-second.)  <small><span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Rjcscott|Rjcscott]] ([[User talk:Rjcscott|talk]] • [[Special:Contributions/Rjcscott|contribs]]) 16:38, 4 August 2009 (UTC)</span></small><!-- Template:Unsigned --> <!--Autosigned by SineBot-->

== Uncertain torque reaction? ==

The article says "There is an uncertain nature of the torque reaction in homopolar machines". What is uncertain about it? Equal and opposite forces occur on the two parts of the electrical circuit, the stator and rotor, and no force occurs on the magnet (unless it happens to be conductive and forms part of the electrical circuit). See "Sources of confusion" in [[homopolar motor]]. -- [[User:D.keenan|D.keenan]] 15:14, 4 December 2006 (UTC)

==Removed references==

[[User:JzG]] removed these applicable references:

* Mike Galloway, "''[http://depalma.pair.com/ N-1 Homopolar Generator]''".
* Bruce E. DePalma, "''[http://www.rexresearch.com/trombly/trombly.htm The Trombly-Kahn Homopolar Generator]; Critique of the N-Machine Constructed by Trombly & Kahn''". 11 October 1985.
* Bruce E. DePalma, "''[http://depalma.pair.com/valone.html A review of: "The Homopolar Handbook", by Thomas Valone]''". 2 February 1995.
* "''[http://www.stardrivedevice.com/over-unity.html The Faraday Disk Dynamo] as the original over-unity device''". Archer Energy Systems, Inc., 2006

[[User:Reddi|J. D. Redding]] 21:59, 11 April 2007 (UTC)

==WikiProject Paranormal==

* [[Bruce DePalma]] and other assorted [[mad scientist]]s. [[User:Reddi|J. D. Redding]]

===Bruce DePalma===
'''Bruce DePalma''' (born '''Bruno James DePalma''') ([[October 2]], [[1935]]&ndash;[[1997]]), son of noted orthopaedic surgeon [[Anthony DePalma]] and elder brother of film director [[Brian De Palma]], was a well known figure in the [[Free energy suppression]] community. 

De Palma claimed that his N-machine [[Homopolar generator]], a device based on the [[Faraday disc]], could produce five times the energy required to run it.  According to mainstream [[physics]], no such device is physically possible. De Palma studied electrical engineering at Harvard (1958) and taught physics at [[MIT]] for 15 years, working under [[Harold Eugene Edgerton]].  He was also employed by [[Edwin H. Land]] of [[Polaroid]] fame.

Bruce De Palma's development of the '''N-machine''' concept in 1977, among his other anomalous devices (at least one of which, De Palma claimed, displayed [[anti-gravity]] characteristics) and the claims surrounding them, set him on a collision course with his more mainstream peers.  His claims of "[[free energy]]" were vigorously refuted over the course of twenty years, by conventional scientists and some members of the alternative energy community alike.

His search for financial backing for the construction of a marketable N-machine saw him relocate from [[Santa Barbara, California]] to [[Australia]] c. 1994, and then [[New Zealand]] in 1996. Probably his greatest ally in his conviction that the N-machine could solve the world's energy and environmental crisis was [[Paramahamsa Tewari]], a Project Director with the [[Indian Nuclear Power Corporation]], with whom he corresponded regularly over many years.  Tewari's [[Space Power Generator]], claimed to be 200% efficient, is based on the same theoretical foundations as the N-machine.

De Palma's death in New Zealand in October 1997 put an end to his most ambitious free energy project, and occurred only weeks prior to the official testing of a device constructed over the course of 6 months in an [[Auckland]] workshop.  The test was attended by, among others, the project's financial backer, Bruce Bornholdt, a prominent [[Wellington]] barrister, as well as the pioneering developer of the [[Adams motor]], Robert Adams (now deceased), who observed the operation of, and measured electrical output from, the N-machine.  This single test failed to demonstrate the [[over-unity]] potential of the N-machine - most of the output energy being lost as heat - and the project was immediately dissolved.

*[[Homopolar generator]]
*[[Perpetual motion]]
*[[History of perpetual motion machines]]
*[[Steorn]]

* [http://depalma.pair.com/index.html THE HOME OF PRIMORDIAL ENERGY], De Palma's website with numerous articles.
* [http://www.mufor.org/nmachine.html Free Energy - The N-Machine]

[[User:Reddi|J. D. Redding]] 22:03, 11 April 2007 (UTC)

You note that DePalma studied at Harvard and taught physics at MIT. Did he graduate from either of these institutions? [[Special:Contributions/104.172.216.137|104.172.216.137]] ([[User talk:104.172.216.137|talk]]) 18:40, 20 April 2017 (UTC)

== Editorial comments by 97.100.194.145 ==

''Please check statement about flux being a vector above. Magnetic flux is a scalar quantity (<math> \int \vec{B} \cdot d\vec{A}</math>), not a vector. Moreover, the Lorentz force law, mentioned below, is derived using Faraday's Law of electromagnetic induction.''

''In all honesty [[Homopolar generator#Physics|this section]] needs to be reviewed.''

(Copied from article. --[[User:Art Carlson|Art Carlson]] ([[User talk:Art Carlson|talk]]) 17:17, 23 January 2008 (UTC))

== Problems with the Homopolar Generator section ==

I recently realized that I do not truly understand how a Faraday disc (I use this spelling on purpose). I am getting on in years so I apologize that my mind may not be working as well Isould lie it to. I find problems with the entry on the Homopolar generator. The entire introductory paragraph is confusing and ambiguous. It really should be rewritten.

The disk does not have to be magnetic. It does not even have to bn conductive unless significant output is required.

The fundamental description arises out of the special theory of relativity (SR). In SR, the fundamental field is a tensor that combines the electric and magnetic vector fields we all know and love into one tensor field usually represented by an antisymmetric 4 x 4 matrix. See the Wikipedia entry for Special relativity.

Given the tensor field (in laboratory coordinates), local motion transforms the tensor to produce an electric field locally at a moving point from the magnetic field present in the laboratory coordinates. Surprise, surprise; this is just the Lorentz force law. I do not yet understand how that fits in with the definition of electric field  F = q E. Does magnetic force F = q v x B arise from F = q E merely  by requiring invariance of the field tensor under a Lorentz transformation?

The electric field produced by motion does not require conductivity. In principle, that electric field should be observable by means of the Stark effect or various electrooptical effects.

More later.

[[User:PEBill|PEBill]] ([[User talk:PEBill|talk]]) 04:50, 25 August 2008 (UTC)

"and a vertical-axis generator could allow the entire rim of a disk to be "brushed" by liquid metal"

I think this should say horizontal axis.  <span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/70.88.177.137|70.88.177.137]] ([[User talk:70.88.177.137|talk]]) 04:32, 12 September 2008 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->


No, he has it correct...
Vertical shaft, means disc's flat to earth, and gravity's influence.
Unless you know of some different kind of liquid metal than we do, lol...  <!-- Template:Unsigned IP --><small class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/47.182.228.198|47.182.228.198]] ([[User talk:47.182.228.198#top|talk]]) 15:14, 27 January 2019 (UTC)</small> <!--Autosigned by SineBot-->

== How it works ==

Parts of the explanation of how it works, described in the Physics section, seem confusing to me. In particular, I find misleading the paragraph starting with "There is a subtle difficulty in this explanation". In my opinion, there is no problem with the Lorentz force explanation. If one raises the question, how can this be reconciled with special relativity, this is what I think. In a moving frame, the electric and magnetic forces get transformed (the transformation laws are described by the [[electromagnetic tensor]]). What appears as a homogeneous magnetic field and no electric field in the reference frame of the stationary machine, appears as a combination of an electric and a magnetic field in the reference frame of an electron moving with the rotating disk. In the reference frame of the electron, the electron responds to this electric field. [[User:Mateat|Mateat]] ([[User talk:Mateat|talk]]) 22:04, 24 October 2009 (UTC)

== Liquid metal brushes and rotation axis orientation ==

From the section above, [[Talk:Homopolar_generator#Problems_with_the_Homopolar_Generator_section]], we had an objection from an unregistered editor:
<blockquote>
"and a vertical-axis generator could allow the entire rim of a disk to be "brushed" by liquid metal"
<br><br />
I think this should say horizontal axis.  <span class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/70.88.177.137|70.88.177.137]] ([[User talk:70.88.177.137|talk]]) 04:32, 12 September 2008 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
</blockquote>

Based on this, {{User|Tkircher}} changed the word to horizontal. This seems to assume that the author intended a pool of liquid metal at the lowest point of a rotor, and that by "the entire rim" was meant "the entire width of the rim". I find this assumption premature. One can conceive a rotor with a vertical axis, disposed in a horizontal plane, with a annular tank of liquid metal under its rim, in which the metal would contact the rotor along the entire circumference. With suitable seals, this tank could be extended to enclosure the rim and seal against the top and bottom of the rotor, thus unambiguously producing the result as claimed, that the <i>entire rim</i> of the disk is contacted by liquid metal. This configuration does not necessarily require that the axis be vertical, though it does relax the mechanical requirements of the seals, as the pressure at the bottom of a tank disposed in a vertical plane would necessarily be greater than that for one disposed in a horizontal plane.
 
Further, the ANU generator, with a vertical axis, used liquid metal brushes in its original configuration. The metal was shot in jets against the rotor, and collected underneath. See [http://physics.anu.edu.au/History/fire_in_the_belly/Fire_in_the_Belly03.pdf Fire in the Belly, Chapter 3: The Big Machine]. Such jets could be arrayed densely enough around the rotor that the liquid metal again, contacts the <i>entire rim</i>.
 
I posit that the result of contacting the entire rim of a homopolar generator with liquid metal in a usable configuration does not depend on the orientation of the rotation axis. Thus, the phrase in quotes above is <b>superfluous</b> and should be removed. [[User:Cstaffa|Cstaffa]] ([[User talk:Cstaffa|talk]]) 03:56, 22 February 2010 (UTC)

I went ahead and changed it because of your suggestion, and I think the article is better for it. You're welcome to change other things if the mood strikes you, of course, that's part of the nature of the thing. [[User:Tkircher|Tkircher]] ([[User talk:Tkircher|talk]]) 06:26, 22 February 2010 (UTC)


Sadly, I just commented on this above, before scrolling down to see an expanded discussion of this niggle.

As I read this, I saw another oversight though...

There is talks of "Seals", where creativity would render them needless.

If the disc/disk was fashioned with an "L" edge, with said "L" facing down, into a trough of liquid metal instead. Only an inner baffle for splash, and an outer "C" casing would be needed. No seal...  <!-- Template:Unsigned IP --><small class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/47.182.228.198|47.182.228.198]] ([[User talk:47.182.228.198#top|talk]]) 15:26, 27 January 2019 (UTC)</small> <!--Autosigned by SineBot-->

== Patents ==

The United States Patent Office uses the clasification class 310 (Electrical generator or motor structure) and subclass 178 (Dynamoelectric; Rotary; D.C.; Homopolar) for these devices. Many of the homopolar patents were obtained prior to 1975. Below is a '''list of homopolar generator patents'''.

===American===
<!-- *  "{{US patent|}} ''''". -->
* G. D. Hathaway,  "{{US patent|5587618}}, ''Direct current homopolar machine''".
* W. F. Weldon, "{{US patent|5530309}} ''Homopolar machine ''". 
* Antonios Challita, "{{US patent|5049771}} ''Electrical machine''".
* W. F. Weldon, "{{US patent|4858304}}, ''Method of constructing a rotor assembly for homopolar generator''". 
* W. F. Weldon, "{{US patent|4800311}} ''Rotor assembly for homopolar generator''".
* W. F. Weldon, "{{US patent|4544874}} ''Homopolar generator power supply system''".
*  W. F. Weldon, "{{US patent|4246507}} ''Removable brush mechanism for a homopolar generator ''". 
* Esko Ensio hubta-Koivisto, "{{US patent|3469137}} ''Electric unipolar motor''".
* E. C. Ketchum and D. H. Andrews, "{{US patent|1082579 }} ''Dynamo electric machine''". 
* A. Kingsbury, "{{US patent|992965}} ''Dynamo electric machine''".
* W. A. Dick,  "{{US patent|992943}} ''Dynamo electric machine''". 
*  [[Jakob E. Noeggerath|J. E. Noeggerath]], "{{US patent|988377}} ''Dynamo electric machine''".
*  H. Hertz,  "{{US patent|988340}} ''Unipolar exciter for turbo-generators''". 
*  D. W. Troy, "{{US patent|979603}} ''Dynamo electric machine''". 
*  A. S. Hubbard, "{{US patent|970827}} ''Dynamo electric machine''". 
*  B. Von Ugrimoff, "{{US patent|970407}} ''Cooling device for electrical sliding contacts''". 
*  E. C. Ketchum, "{{US patent|966839}} ''Brush holders for dynamos''".
*  J. E. Noeggerath, "{{US patent|960383}} ''Dynamo electric machine''". 
*  J. E. Noeggerath, "{{US patent|959959}} ''Dynamo electric machine''". 
*  J. E. Noeggerath, "{{US patent|937462}} ''Dynamo electric machine''". 
*  J. E. Noeggerath, "{{US patent|920626}} ''Dynamo electric machine''". 
*  J. E. Noeggerath,  "{{US patent|900771}} ''Armature for unipolar machines''".
*  J. E. Noeggerath, "{{US patent|895888}} ''Unipolar dynamo electric machine''". 
*  J. E. Noeggerath, "{{US patent|895887}} ''Acyclic machine''".
*  J. E. Noeggerath, "{{US patent|890697}} ''Protective device for unipolar machine''". 
*  A. C. Eastwood, "{{US patent|881387}} ''System of control for electric motors''". 
*  J. E. Noeggerath, "{{US patent|873072}} ''Dynamo electric machine''".  
*  W. Mathiesen, "{{US patent|861192}} ''Unipolar dynamo''". 
*  [[Elihu Thomson|E. Thomson]], "{{US patent|859350}} ''Unipolar generator''". 
*  J. E. Noeggerath, "{{US patent|854756}} ''Dynamo electric machine''".  
*  C. Macmillan, "{{US patent|854749}} ''Power transmission mechanism''". 
*  C. Macmillan, "{{US patent|850664}} ''Dynamo electric machine''".  
*  J. E. Noeggerath, "{{US patent|832742}} ''Unipolar alternating current machine''". 
*  E. C. Ketchum, "{{US patent|826668}} ''Dynamo''". 
*  H. H. Wait, "{{US patent|806217}} ''Dynamo electric machine''". 
*  J. E. Noeggerath, "{{US patent|805315}} ''Unipolar machine''".  
*  [[Charles Proteus Steinmetz|C. P. Steinmetz]], "{{US patent|804440}} ''Dynamo electric machine''". 
*  J. E. Noeggerath, "{{US patent|789444}} ''Electric motor''". 
*  E. R. Cox, Jr., "{{US patent|742600}} ''Dynamo electric machine or motor''". 
*  B. Bjarnason, "{{US patent|678157}} ''Dynamo electric machine''". 
*  F. W. Throop, "{{US patent|662042}} ''Dynamo electric machine''". 
*  G. Dalen and A Hultovist, "{{US patent|645943}} ''Dynamo electric machine''". 
*  F. G. Mayer, "{{US patent|561803}} ''Dynamo electric machine''". 
*  E. Thomson and M. J. Wightman, "{{US patent|550464}} ''Dynamo electric machine''".
*  G. Rennerfelt, "{{US patent|523998}} ''Dynamo electric machine''". 
*  H. E. Dikeman, "{{US patent|518444}} ''Dynamo electric machine''". 
*  J. E. Maynadier, "{{US patent|515882}} ''Dynamo electric machine''".
*  T. L. Willson, "{{US patent|495538}} ''Dynamo electric machine''". 
*  [[Nikola Tesla|N. Tesla]], "{{US patent|406968}} ''Dynamo electric machine''". 
*  J. B. Entz, "{{US patent|400838}} ''Dynamo electric machine". 
*  [[Rudolf Eickemeyer|R. Eickemeyer]], "{{US patent|396149}} ''Unipolar dynamo electric machine''".  
*  [[Elmer Ambrose Sperry|E. A. Sperry]], "{{US patent|354946}} ''Dynamo electric machine".
*  R. Eickemeyer, "{{US patent|352234}} ''Electro magnetic and megneto electric machine". 
*  R. Eickemeyer, "{{US patent|351907}} ''Device for taking electric currents from or to moving surfaces''". 
*  R. Eickemeyer, "{{US patent|351904}}  ''Magneto electric and electro magnetic machine''". 
*  R. Eickemeyer, "{{US patent|351903}}  ''Magneto electric and electro magnetic machine''".  
*  R. Eickemeyer, "{{US patent|351902}} ''Magneto electric and electro magnetic machine''". 
*  R. Eickemeyer, "{{US patent|342589}} ''Dynamo electric and electro magnetic machine''". 
*  R. Eickemeyer, "{{US patent|342588}} ''Dynamo electric and electro magnetic machine''".
*  R. Eickemeyer, "{{US patent|342587}} ''Dynamo electric and electro magnetic machine''". 
*  R. Eickemeyer, "{{US patent|342504}} ''Magneto electric and electro magnetic machine". 
*  [[Sebastian Ziani de Ferranti|S. Z. De Ferranti]], "{{US patent|341097}} ''Unipolar dynamo electric machine''".   
*  [[Charles Batchelor|C. Batchelor]] and H. E. Walter"{{US patent|339839}} ''Dynamo electric machine''".
*  C. Hering, "{{US patent|339772}} ''Unipolar dynamo electric machine''".  
*  [[George Forbes (scientist)|G. Forbes]], "{{US patent|338169}} ''Dynamo electric machine''". 
*  A. E. G. Lubke, "{{US patent|293758}} ''Dynamo electric machine''". 
*  A. F. Delafield, "{{US patent|278516}} ''Dynamo electric machine''". 
*  C. E. Ball, "{{US patent|238631}} ''Dynamo or magneto-electric machine''".

--[[User:Reddi|J. D. Redding]] 17:04, 3 August 2013 (UTC)

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