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Topic: Magnetic dipole

	Dipole -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-22)
		Dipoles can be characterized by their dipole (A particular point in time) moment, a vector quantity with a magnitude equal to the product of the charge or magnetic strength of one of the poles and the distance separating the two poles.
		The direction of the dipole moment corresponds to the direction from the negative to the positive charge or from the (The region of the United States lying south of the Mason-Dixon Line) south to the (The northernmost point of the Earth's axis) north pole.
		Instantaneous dipoles: These occur due to chance when (An elementary particle with negative charge) electrons happen to be more concentrated in one place than another in a ((physics and chemistry) the simplest structural unit of an element or compound) molecule, creating a temporary dipole.
	www.absoluteastronomy.com /encyclopedia/d/di/dipole.htm (986 words)

	Method for manufacturing a magnetic dipole antenna - US Patent 6675461 (Site not responding. Last check: 2007-10-22)
		The magnetic dipole antenna 130 has the transmission line 125 that is connected to a test equipment (not shown) for measuring the frequency produced from the gap, z 126, between the top plate 124 and the middle plate 123.
		A magnet 131, electromagnet, or a material that produces magnetic attraction, exerts force upon the top plate 124 of the magnetic dipole antenna 130 for tuning, until a desirable frequency is measured by the test equipment.
		The magnetic dipole antenna 140 has the transmission line 125 that is connected to a test equipment (not shown) for measuring the frequency produced from the gap, z 126, between the top plate 124 and the middle plate 123.
	www.patentstorm.us /patents/6675461.html (4313 words)

	Magnetic moment (Site not responding. Last check: 2007-10-22)
		These relationships for a finite current loop extend to the magnetic dipoles of electron orbits and to the intrinsic magnetic moment associated with electron spin.
		The direction of the magnetic moment is perpendicular to the current loop in the right-hand-rule direction, the direction of the normal to the loop in the illustration.
		The position where the magnetic moment is opposite to the magnetic field is said to have a higher magnetic potential energy.
	hyperphysics.phy-astr.gsu.edu /hbase/magnetic/magmom.html (300 words)

	Earth's magnetic field - Open Encyclopedia (Site not responding. Last check: 2007-10-22)
		The field is approximately a magnetic dipole, with one pole near the geographic north pole and the other near the geographic south pole.
		The magnetic field of a bar magnet, or any other type of permanent magnet, is created by the coordinated motions of electrons (negatively charged particles) within iron atoms.
		Also, since a magnetic field reversal has never been observed by humans and the mechanism of field generation is not well understood, it is difficult to say what the characteristics of the magnetic field might be leading up to such a reversal.
	open-encyclopedia.com /Earth%27s_magnetic_field (735 words)

	Electromagnetic propagation tool using magnetic dipole antennas - Patent 5491488
		The tool of claim 7 wherein each of said three circumferentially spaced transmitting magnetic dipole antennas are in substantial axial alignment with a corresponding one of each of said three circumferentially spaced near receiving magnetic dipole antennas and with a corresponding one of each of said three circumferentially spaced far receiving magnetic dipole antennas.
		The tool of claim 1 wherein the circumference of said small current loop dipole antenna of said transmitting magnetic dipole antenna and the circumference of said small current loop dipole antenna of said receiving magnetic dipole antenna are each between about 10% and about 20% of the circumference of said drill collar segment.
		Further, the three voltage ratios of the three receiver dipole pairs (i.e., dipole antennas 78 and 90 are a first axially aligned pair, dipole antennas 80 and 92 are a second axially aligned pair and dipole antennas 82 and 94 are a third axially aligned pair) should be same.
	www.freepatentsonline.com /5491488.html (5916 words)

	What is a magnetic field? (Site not responding. Last check: 2007-10-22)
		A magnet produces a vector field, the magnetic field, at all points in the space around it.
		A magnetic field can also be created by the spin magnetic dipole moment, and by the orbital magnetic dipole moment of an electron within an atom.
		By convention, we state that the magnetic field has a direction associated with it, such that the field exits the North end of a magnet, flows through the air or other materials nearby, and re-enters the South end of the magnet.
	my.execpc.com /~rhoadley/magfield.htm (718 words)

	Torque on a Magnetic Dipole and Electric Motors (Site not responding. Last check: 2007-10-22)
		In analogy with the electric dipole in an electric field, the potential energy of a magnetic dipole in a magnetic field is
		At this point either the magnetic field is reversed by some mechanism or the magnetic dipole is reversed by making the current circulate around the loops in the opposite direction.
		The torque due to the magnetic force then turns the axle through another half-turn, whereupon the field or the magnetic moment is again reversed, and so on.
	www.physics.nmt.edu /~raymond/classes/ph13xbook/node163.html (344 words)

	[No title]
		In a bar magnet, there is a north pole and a south pole, and this field is said to be "dipole".
		In 1971, Barnes pointed out that, according to the data he had, the strength of the dipole component of the earth's magnetic field (measured in a unit known as a "gauss") has decreased between six and seven percent since it was first measured in 1835.
		During this time, the sun's magnetic dipole field decreased in strength, dropped to almost nothing for a period of several years, and re-emerged with reversed polarity.
	www.geocities.com /CapeCanaveral/Hangar/2437/magnetic.htm (1249 words)

	Notch fed magnetic microstrip dipole antenna with shorting pins - Patent 4040060
		A notch fed magnetic microstrip dipole antenna consisting of a thin electally conducting, rectangular-shaped radiating element formed on one surface of a dielectric substrate, the ground plane being on the opposite surface with the radiating element shorted to the ground plane.
		Reference is made to the "magnetic microstrip dipole" instead of simply the "microstrip dipole" to differentiate between two basic types; one being the magnetic microstrip type, and the other being the electric microstrip type.
		The magnetic microstrip antenna consists essentially of a conducting strip called the radiating element and a conducting ground plane separated by a dielectric substrate, with the radiating element having one end shorted to the ground plane.
	www.freepatentsonline.com /4040060.html (3941 words)

	12. Theory of Biomagnetic Measurements
		As in the case of the detection of the electric dipole moment of a volume source, Section 11.6.9, both unipolar and bipolar leads may be used in synthesizing the ideal lead field for detecting the magnetic dipole moment of a volume source.
		Because in an infinite homogeneous volume conductor the magnetic lead field flow lines encircle the symmetry axis, it is easy to calculate the sensitivity distribution of a magnetic lead in a cylindrically symmetric volume conductor, whose symmetry axis coincides with the magnetometer axis.
		The magnetic field of a source close to one of the coils produces a stronger signal in the proximal coil (i.e., the coil closer to the source) than in the distal coil (farther from the source), and the difference of these fields is detected.
	butler.cc.tut.fi /~malmivuo/bem/bembook/12/12.htm (8893 words)

	ipedia.com: Dipole Article (Site not responding. Last check: 2007-10-22)
		A dipole is a pair of electric charges or magnetic poles of equal magnitude but opposite polarity, separated by some (usually small) distance.
		speaking a dipole contains only two point charges (or magnetic poles), however various arrangements of multiple charges or currents have dipole moments and may be treated as an effective dipole.
		The physical chemist Peter J. Debye was the first scientist to study molecular dipoles extensively, and dipole moments are consequently measured in units named debyes in his honor.
	www.ipedia.com /dipole.html (554 words)

	Magnetic Field
		To determine the magnetic force on an ionised atom or molecule the magnetic field must be known.
		However, the ways in which these magnetic dipoles interact with each other and external fields is important in the interpretation of the spectroscopic behaviour of atoms and molecules.
		The dipole is placed in a uniform field so that edges 2 and 4 are perpendicular to the field lines and 1 and 3 are oriented at an angle φ (not shown on figure).
	www.dac.neu.edu /physics/b.barbiellini/phy1302/magnetic.htm (1344 words)

	Specific Arguments - Magnetic Field
		The dipole field is not an accurate measurement of the overall strength of the earth's magnetic field.
		This implies that the value of the dipole field could not have been much greater in the past, since it is limited by the total magnetic energy, which does not change very rapidly.
		Studies of the magnetic field as recorded in dated rocks and pottery have shown that the dipole moment actually fluctuates over periods of a few thousand years and that decreases in field intensity are eventually followed by increases.
	www.infidels.org /library/modern/dave_matson/young-earth/specific_arguments/magnetic_field.html (1735 words)

	Earth's magnetic field
		The magnetic field extends several tens of thousands of kilometers into space.
		The Earth's magnetic field reverses at intervals, ranging from tens of thousands to many millions of years, with an average intervals of ~250,000 years.
		Some scientists have produced models for the core of the Earth wherein the magnetic field is only quasi-stable and the poles can spontaniously migrate from one orientation to the other over the course of a few hunderd to a few thousand years.
	www.brainyencyclopedia.com /encyclopedia/e/ea/earth_s_magnetic_field.html (780 words)

	Field Lines for a Magnetic Dipole (Site not responding. Last check: 2007-10-22)
		Another way to visualize the magnetic force field associated with a magnetic dipole is to plot the field lines for the force.
		Shown below is the spatial variation of the magnetic force (green arrows)* associated with a magnetic dipole and a set of field lines (red lines) describing the force.
		Where adjacent red lines are closely spaced, such as near the two monopoles (blue and yellow circles) comprising the dipole, the magnetic force is large.
	www.geo.ucalgary.ca /~maillol/goph365/mag/fieldl.html (260 words)

	Magnetic properties of solids
		Materials may be classified by their response to externally applied magnetic fields as diamagnetic, paramagnetic, or ferromagnetic.
		Another way to deal with the magnetic fields which arise from magnetization of materials is to introduce a quantity called magnetic field strength H.
		All atoms have inherent sources of magnetism because electron spin contributes a magnetic moment and electron orbits act as current loops which produce a magnetic field.
	hyperphysics.phy-astr.gsu.edu /hbase/solids/magpr.html (564 words)

	AGU Web Site: EiS. How Are Geomagnetic Reversals Related to Field Intensity?
		This scenario of a coming attempt by Earth's magnetic field to reverse its polarity is suggested by direct observation of the field since the 19th century and laboratory investigation of historic lavas and other fired materials that record the ambient field while cooling.
		According to the model, this occurs when dipole strength, assumed to vary in a sinusoidal wavelike manner, is at an intensity low.
		The dipole polarity state of the geomagnetic field in which north-seeking compass needles point to the north (south).
	www.agu.org /sci_soc/hoffman.html (1019 words)

	The Earth’s Magnetic Field is Still Losing Energy
		Dipole and non-dipole magnetic fields from bar magnets: (a) dipole, (b) quadrupole, and (c) octopole.
		Although magnetic fields and energies also exist in the core as well as outside it, observations of the field outside the core cannot determine the field in the core.
		Table II and Figure 4 show the energies contained in the earth’s magnetic field from the years 1900 to 2000, according to the IGRF data (of which Table I is a sample) and equations (8), (10), and (11).
	www.creationresearch.org /crsq/articles/39/39_1/GeoMag.htm (5735 words)

	Basic Relationships
		The strength of a dipole depends on strength of magnetization of poles and their separation, and is a vector quantity known as dipole moment, which is analogous to mass in gravity:
		Magnetic dipole moment is an extensive quantity (like mass).
		In analogy with gravity, magnetic dipole moment per unit volume is an intensive quantity (like density).
	geophysics.ou.edu /solid_earth/notes/mag_basic/mag_basic.html (576 words)

	magnetic dipole -- Encyclopædia Britannica
		generally a tiny magnet of microscopic to subatomic dimensions, equivalent to a flow of electric charge around a loop.
		Electrons circulating around atomic nuclei, electrons spinning on their axes, and rotating positively charged atomic nuclei all are magnetic dipoles.
		The sum of these effects may cancel so that a given type of atom may not be a magnetic dipole.
	www.britannica.com /eb/article-9050021?tocId=9050021 (68 words)

	Off axis field due to a magnetic dipole moment
		B is the magnetic field, in teslas, at any point in space that isn't at the origin.
		A magnetic dipole moment is a simple mathematical representation of a coil, electromagnet or permanent magnet ("refrigerator magnet") that can be used to predict the magnetic field at a distance from its source.
		is the "intrinsic induction" of the magnet, in teslas,
	www.netdenizen.com /emagnet/offaxis/mmoffaxis.htm (533 words)

	Magnetic Field (Site not responding. Last check: 2007-10-22)
		The connection between electric current and magnetic field was first observed when the presence of a current in a wire near a magnetic compass affected the direction of the compass needle.
		The axis of the bar magnet is perpendicular to the plane of the loop and passes through the center of the loop.
		(c) In a magnetic field the torque on a bar magnet tends to align the magnet's dipole moment with the direction of the B field.
	www.physics.sjsu.edu /facstaff/becker/physics51/mag_field.htm (1557 words)

	The Sun Does a Flip
		The Sun's magnetic poles will remain as they are now, with the north magnetic pole pointing through the Sun's southern hemisphere, until the year 2012 when they will reverse again.
		Scientists call such a field a "dipole." The Sun's dipolar field is about as strong as a refrigerator magnet, or 50 gauss (a unit of magnetic intensity).
		The Sun's magnetic field envelops the entire solar system in a bubble that scientists call the "heliosphere." The heliosphere extends 50 to 100 astronomical units (AU) beyond the orbit of Pluto.
	science.nasa.gov /headlines/y2001/ast15feb_1.htm (1190 words)

	A review of magnets and magnetism (Site not responding. Last check: 2007-10-22)
		A magnet is an object made of certain materials which create a magnetic field.
		This is an example of a magnetic dipole ("di" means two, thus two poles).
		To learn more about magnets and magnetism, you should spend some time reading articles about magnets in encyclopedias at home or on the web, other related websites and other books.
	my.execpc.com /~rhoadley/magencyc.htm (896 words)

	Magnetic Dipole Radiation From A Sinusoidally Varying Dipole--The Near/Transition Zone (Site not responding. Last check: 2007-10-22)
		The field lines of a magnetic dipole for the case where the dipole varies sinusoidally in time by 10% in amplitude (20% peak to peak).
		That is, the dipole is always oriented along the vertical axis, and its dipole moment varies in time in a manner proportional to (1.0 + 0.1 sin(2 Pi t/T)).
		In this animation we let the dipole moment vary from -1 to 1 sinusiodally, a more realistic animation of radiation from an antenna with an AC feed.
	web.mit.edu /jbelcher/www/sin.html (270 words)

	Physics Tutoring: Magnetism in Matter (Site not responding. Last check: 2007-10-22)
		When the material is placed in a magnetic field, the domains align in the direction of the field, thereby magnetizing the substance.
		A: The end of a magnetic needle of a compass that points toward the magnetic North pole of the earth is the South pole of the needle.
		Ferromagnetic materials: materials, in the absence of an external magnetic field, in which some of the electrons have their magnetic dipole moments aligned by means of a quantum physical interaction called exchange coupling, producing regions (domains) within the material with strong magnetic dipole moments.
	www.slcc.edu /schools/hum_sci/physics/tutor/2220/magnetism_in_matter (667 words)

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