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Magentic poles

Magenetic fields

Magnetic domains


All the help is appreciated. I do aeard the most points for the right answers. I wish there is a way to award everyone that gives the right answers the best answer.

2006-06-09 13:25:38 · 3 answers · asked by Anonymous in Education & Reference Homework Help

I already have the DICTIONARY definition. What I need is an explanation from a scientific view.

2006-06-09 13:30:42 · update #1

So, then magentic effects are observed in a region around matter called the magnetic DOMAIN or FIELD???? I'm pretty sure it isn't POLE.

2006-06-09 13:40:02 · update #2

3 answers

pole
magnetic pole, the two nearly opposite ends of the planet where the earth's magnetic intensity is the greatest, as the north and south magnetic poles. For the magnetic north, it is the direction from any point on the earth's surface linking the horizontal component of the magnetic lines of force with the observer and north magnetic pole; it is similar for magnetic south. The north magnetic pole, first located (1831) by English explorer Sir James C. Ross, is now about 78°N and 104°W in the Queen Elizabeth Islands of northern Canada. The south magnetic pole, reached (1909) by English geologists Sir T. W. E. David and Sir Douglas Mawson, is now about 66°S and 139°E on the Adélie Coast of Antarctica. The magnetic poles are not fixed but follow circular paths with diameters of about 100 miles (160 km). Studies of paleomagnetism also indicate that the earth's magnetic field has reversed its polarity many times in the geologic past. The best hypothesis to date for the origin of terrestrial magnetism is the self-exciting dynamo theory, where the earth's magnetic field is generated by the interaction of motion and electrical currents in the earth's liquid outer core.

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Magnetic fields are produced by the motion of electrical charges. For example, the magnetic field of a bar magnet results from the motion of negatively charged electrons in the magnet. The origin of the Earth's magnetic field is not completely understood, but is thought to be associated with electrical currents produced by the coupling of convective effects and rotation in the spinning liquid metallic outer core of iron and nickel. This mechanism is termed the dynamo effect.
Rocks that are formed from the molten state contain indicators of the magnetic field at the time of their solidification. The study of such "magnetic fossils" indicates that the Earth's magnetic field reverses itself every million years or so (the north and south magnetic poles switch). This is but one detail of the magnetic field that is not well understood

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In order to explain the fact that ferromagnetic materials with spontaneous magnetisation could exist in the demagnetised state Weiss proposed the concept of magnetic domains. Weiss built on earlier work carried out by Ampère, Weber and Ewing suggesting their existence. The findings of this work revealed that within a domain large numbers of atomic moments are aligned typically 1012-1018, over a much larger volume than was previously suspected. The magnetisation within the domain is saturated and will always lie in the easy direction of magnetisation when there is no externally applied field. The direction of the domain alignment across a large volume of material is more or less random and hence the magnetisation of a specimen can be zero.

Magnetic domains exist in order to reduce the energy of the system. A uniformly magnetised specimen as shown in figure 5(a) has a large magnetostatic energy associated with it. This is the result of the presence of magnetic free poles at the surface of the specimen generating a demagnetising field, Hd. From the convention adopted for the definition of the magnetic moment for a magnetic dipole the magnetisation within the specimen points from the south pole to the north pole, while the direction of the magnetic field points from north to south. Therefore, the demagnetising field is in opposition to the magnetisation of the specimen. The magnitude of Hd is dependent on the geometry and magnetisation of the specimen. In general if the sample has a high length to diameter ratio (and is magnetised in the long axis) then the demagnetising field and the magnetostatic energy will be low.

The break up of the magnetisation into two domains as illustrated in figure 5(b) reduces the magnetostatic energy by half. In fact if the magnet breaks down into N domains then the magnetostatic energy is reduced by a factor of 1/N, hence figure 5(c) has a quarter of the magnetostatic energy of figure 5(a). Figure 5(d) shows a closure domain structure where the magnetostatic energy is zero, however, this is only possible for materials that do not have a strong uniaxial anisotropy, and the neighbouring domains do not have to be at 180º to each other.

2006-06-09 13:31:37 · answer #1 · answered by cmhurley64 6 · 2 0

magnet is what sticks to the metal.
pole is a vertically standing rod.
field is a open space you can walk on.
domain is a relm.

2006-06-09 20:31:31 · answer #2 · answered by edhchoe 3 · 0 0

Do your own homework.! Look it up!

2006-06-09 20:29:08 · answer #3 · answered by Åⓝⓞⓝⓨⓜⓞⓤ§ 4 · 0 0

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