Talk:Dynamo theory

message: With respect to energy generation couldn't a dynamo-based "appropriate technology" (see Wiki entry on this) be even better than "solar" (at least for many situations), from the standpoint that "the sun wouldn't even need to shine" (not all the time) to generate some electrical current with a "dynamo" device.  The "bicycle hub" units are OK, but I think the scale could be larger and the device would remain "appropriate".  Peace, Ken Hausle - kjh-es.com. 12:44 pm (eastern) Charlotte, NC. KenH
Wrong sort of dynamo Stevelinton (talk) 23:35, 21 August 2010 (UTC)
thread_title: Dynamo on a larger scale

message: From The Sunday Times  June 14, 2009
Oceans charge up new theory of magnetism
"A radical new idea may revolutionise our understanding of one of the most vital forces on Earth
Jonathan Leake
Earth's magnetic field, long thought to be generated by molten metals swirling around its core, may instead be produced by ocean currents, according to controversial new research published this week.
It suggests that the movements of such volumes of salt water around the world have been seriously underestimated by scientists as a source of magnetism.
If proven, the research would revolutionise geophysics, the study of the Earth’s physical properties and behaviour, in which the idea that magnetism originates in a molten core is a central tenet.
Earth’s magnetic field is vital for life, extending tens of thousands of miles into space and protecting the planet against radiation that would otherwise burn away the atmosphere and oceans.... -snip-  "
For more information go to
http://www.iop.org/News/news_35352.html / http://physicsworld.com/cws/article/news/39469/ / http://www.iop.org/EJ/abstract/1367-2630/11/6/063015  —Preceding unsigned comment added by Rpauli (talk • contribs) 05:16, 15 June 2009 (UTC)
thread_title: Are ocean currents the cause

message: There is a lot of high octane information here, but we need a better opening that describes the basics. I propose the following though I am happy to defer to those better acquainted with the physics.
 A dynamo requires a molten outer core that contains iron and flows in convective loops, as well as a solid inner core that also contains iron.  The magnetic field results from the interaction between the flowing and stationary iron.  Since the flow can change in time, so can the magnetic field; it is not fixed like bar magnet. The field shifts slowly so that the difference between magnetic north and true north (defined by axis of rotation) changes measurably during a human life span.  Changes in the dynamo also drive geomagnetic reversals, (wiki ref) when the north magnetic pole weakens then reestablishes in the south and visa versa, which occur at irregular intervals ranging from hundreds of thousands to tens of millions of years. 
 The magnetic field created by the dynamo, does a lot more than your compasses work and provide navigation for migrating birds. The convective heat flow necessary for plate tectonics is what drives the dynamo. Without this convective churning there would be no continents, no mountains, and our planet would be covered with water. So there is a strong tie between the long term existence of a dynamo and life as we know it.
 Of the eight planets, only the terrestrial planets (the first four) have iron cores.  Of these, Mercury and Venus do not have dynamos, and have no magnetic fields.  Mars appears to have had a dynamo in the past, but the convective movement has stopped. Currently, Earth is the only plant in our solar system that has a magnetic pole. 
 
R Stillwater (talk) 22:47, 28 October 2008 (UTC)
replies: text: There's a lot wrong with that proposal, eg. Jupiter has a stronger mag field, thought be due to metallic hydrogen not iron. See Magnetosphere_of_Jupiter. - Rod57 (talk) 09:51, 22 May 2018 (UTC)

text: The power for the dynamo ultimately comes from the rotation of the Earth and the heat sources in the inner core. The effect of Lentz's law is that the moving conductors "carry" the magnetic field with them. The complex motions in the rotating convecting fluid then twist the field up in all sorts of strange ways, and complex and unexpected behaviour follows. Lentz's law is not being violated. Stevelinton (talk) 23:35, 21 August 2010 (UTC)
thread_title: Description of Dynamo

message: The "Iron Dynamo"theory for the Earth's magnetism conflicts with a basic law of electricity and magnetism.
It is called Lenz's Law. When a conductor moves in a  magnetic field a current is induced in the conductor. The induced current will generate a magnetic field. The polarity of the magnetic field generated is opposite to the magnetic field which caused the current to be generated.  In simple terms a magnetic field change cannot create a current that in turn creates a magnetic field that supports the original change. It such a thing was possible, it would be the magnetic equivalent of perpetual motion. No application of Maxwell's mathematics can change the laws of electricity and magnetism.
[Lenz's Law is included in all elementary textbooks explaining electricity and magnetism.]
Wilf James 11:30 GMT 10 February 2009  —Preceding unsigned comment added by 86.11.15.76 (talk) 11:36, 10 February 2009 (UTC)
replies: text: The power for the dynamo ultimately comes from the rotation of the Earth and the heat sources in the inner core. The effect of Lentz's law is that the moving conductors "carry" the magnetic field with them. The complex motions in the rotating convecting fluid then twist the field up in all sorts of strange ways, and complex and unexpected behaviour follows. Lentz's law is not being violated. Stevelinton (talk) 23:35, 21 August 2010 (UTC)
thread_title: Conflict with Lentz's law ?

message: Need a link for ohmic decay RJFJR (talk) 19:40, 9 November 2009 (UTC)
thread_title: ohmic decay 

message: It may seem surprising that I downgraded the apparently well-sourced statement about Einstein to a rumor in a footnote. However, I have some inside knowledge on this. The statement was originally made in The earth's magnetic field : its history, origin, and planetary perspective by Merrill and McElhinny, and because of its source has been repeated many times in reliable publications. However, Merrill himself recently realized that he didn't know where he got this statement from, and hasn't been able to find a source. See also footnote 23 for Chapter 2 in Our Magnetic Earth by Merrill. RockMagnetist (talk) 13:38, 16 October 2011 (UTC)
thread_title:  Einstein 

message: Please explain in more detail (ideally with images as well as words) how the Coriolis force changes convection currents in the outer core into rolls of electric currents.  Jray310 (talk) 10:07, 15 May 2016 (UTC)
thread_title:  Coriolis force  

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thread_title:  External links modified 

message: The Moon thought to play a major role in maintaining Earth's magnetic field (based on The deep Earth may not be cooling down) says tidal forces could provide the energy to keep the Earths core hot and moving. Has this been confirmed or debunked ? - Rod57 (talk) 09:36, 22 May 2018 (UTC)
thread_title:  2016 suggestion that the moon is significant via tidal forces 

message: I  propose adding more detailed information about numerical dynamo modelling. I will be adding new information to the current section to try to achieve this. I will also add three figures, but if they crowd the page too much, it may be better to leave the page without them. Rojasmar (talk) 23:46, 14 March 2019 (UTC)
thread_title:  Updating "Numerical models" section 

message: सक्रिय चर्चाएँ 106.76.93.43 (talk) 21:46, 7 January 2023 (UTC)
thread_title:  सक्रिय चर्चाएँ