19665729 magnetic materials

8/3/2019 19665729 Magnetic Materials

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QBA Miguel A. Castro Ramrez


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Magnetic FieldsMagnetic Fields

The region where the magnetic forces act isThe region where the magnetic forces act is

called the magnetic fieldcalled the magnetic field


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EARTHS

MAGNETISMThe Earth itself has a huge

magnetic field - as if it had a

huge bar magnet embedded

at its centre. The Earthsmagnetic field lines emerge

from near the geographical

north pole and re-enter it at

the south pole. The nature of

the field around the Earthvaries in both strength and

direction. The Earths

magnetic field is strongest at

the magnetic poles andweakest near the Equator.


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Why does the Earth have a magnetic field?

The Earth has, at its centre, adense liquid core, of abouthalf the radius of the Earth,with a solid inner core. Thiscore is though to be mostly

made of molten iron andnickel perhaps mixed withsome lighter elements.Circulating ions of iron and

nickel in highly conductingliquid region of earths coremight be forming currentloops and producing earthsmagnetism.


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The Earths magnetic field


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Magnetic ElementsMagnetic Elements

Magnetic DeclinationMagnetic Declination

Magnetic Inclination or MagnMagnetic Inclination or Magn


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Magnetic DeclinationMagnetic Declination

The small angleThe small angle

between magneticbetween magnetic

axis andaxis and

geographic axis atgeographic axis at

a place is defineda place is defined

as the magneticas the magneticdeclinationdeclination..


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Magnetic Inclination orMagnetic Inclination or

Magnetic DipMagnetic Dip The angle whichThe angle which

the direction ofthe direction of

total strength oftotal strength ofearths magneticearths magneticfield makes withfield makes with

a horizontal linea horizontal linein magneticin magneticmeridian.meridian.


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Atoms themselves have magnetic propertiesdue to the spin of the atoms electrons.

These areas of atoms are called domains

Groups of atoms join so that their

magnetic fields are all going in the samedirection


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en an unmagnetized substance is placed in a magnen an unmagnetized substance is placed in a magne

field, the substance can become magnetized.field, the substance can become magnetized.

is happens when the spinning electrons line up in this happens when the spinning electrons line up in thsame direction.same direction.


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The metals affected byThe metals affected bymagnetism consist of tinymagnetism consist of tinyregions called 'Domains'regions called 'Domains'which behave like tinywhich behave like tiny

magnets. Normally they aremagnets. Normally they arearranged in the magneticarranged in the magneticmaterial all pointing inmaterial all pointing indifferent directions in adifferent directions in acompletely random fashioncompletely random fashionand so their magnetic effectsand so their magnetic effectscancel each other out. If ancancel each other out. If anobject is magnetized it isobject is magnetized it isbecause the domains are allbecause the domains are allmade to point in the samemade to point in the samedirection. This can be done bydirection. This can be done by

stroking the magneticstroking the magneticmaterial with a magnet (ormaterial with a magnet (ormagnets) as shown in themagnets) as shown in thediagram. When aligned thediagram. When aligned thedomains reinforce onedomains reinforce oneanother and create north andanother and create north and

south poles at either end.south poles at either end.


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Classification ofClassification of

magnetic materialsmagnetic materials Diamagnetic SubstancesDiamagnetic Substances

Paramagnetic substancesParamagnetic substances

Ferromagnetic substancesFerromagnetic substances


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Diamagnetic substancesDiamagnetic substances

The diamagnetic substances are those inThe diamagnetic substances are those inwhich the individual atoms or ions do notwhich the individual atoms or ions do not

possess any net magnetic moment onpossess any net magnetic moment ontheir own.their own.

When such substances are placed in anWhen such substances are placed in an

external magnetizing field, they get feeblyexternal magnetizing field, they get feeblymagnetized in a direction opposite to amagnetized in a direction opposite to a

magnetizing field.magnetizing field.


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Paramagnetic SubstancesParamagnetic Substances

Paramagnetic substances are those inParamagnetic substances are those in

which each individual atom or molecule orwhich each individual atom or molecule or

ion has a net non zero magnetic momention has a net non zero magnetic momentof its own.of its own.

When such substances are placed in anWhen such substances are placed in an

external magnetic field, they get feeblyexternal magnetic field, they get feeblymagnetized in the direction of themagnetized in the direction of the

magnetizing field.magnetizing field.


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Ferromagnetic materialsFerromagnetic materialsFe rroma gnet ice rroma gnet icDomains inom ains inMaterialsaterials FerromagneticFerromagnetic

material are thosematerial are those

in which eachin which each

individual atom orindividual atom or

molecule has amolecule has a

non zero magneticnon zero magnetic

momentmoment


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Hysteresis CurveHysteresis Curve

The relationship between magnetic fieldThe relationship between magnetic field

strength (H) and magnetic flux density (B) willstrength (H) and magnetic flux density (B) will

follow a curve up to a point where furtherfollow a curve up to a point where further

increases in magnetic field strength will resultincreases in magnetic field strength will result

in no further change in flux density. Thisin no further change in flux density. This

condition is calledcondition is called magnetic saturationmagnetic saturation tilltill

point (a)point (a)


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the plotted relationship will follow athe plotted relationship will follow adifferent curve back towards zero fielddifferent curve back towards zero field

strength at which point it will be offsetstrength at which point it will be offset

from the original curve by an amountfrom the original curve by an amount

called thecalled the remanent flux densityremanent flux densityoror

RetentityRetentity as shown in graph at point (b)as shown in graph at point (b)

The 'thickness' of the middle, describesThe 'thickness' of the middle, describesthe amount of hysteresis, related to thethe amount of hysteresis, related to the

coercivitycoercivity of the material as from (c) to (f)of the material as from (c) to (f)


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Hysteresis curve of softHysteresis curve of soft

and steeland steelThe retentivity ofThe retentivity of

soft iron >soft iron >retentivity of steelretentivity of steel

Soft iron is moreSoft iron is morestronglystronglymagnetized thanmagnetized thansteelsteel

Coercivity of softCoercivity of softiron < Coercivity ofiron < Coercivity ofsteelsteel

Hence, soft ironHence, soft iron


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electromaelectroma

gnetgnet A soft iron rod has noA soft iron rod has nomagnetic fieldmagnetic field

When current flows inWhen current flows in

the wire the soft ironthe wire the soft ironbecomes magnetized sobecomes magnetized so

a magnetic field isa magnetic field is

detected by the plottingdetected by the plotting

compasses.compasses.


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THANK YOUTHANK YOU

Efforts By :-Efforts By :-Lovish UppalLovish Uppal

Rajat VermaRajat Verma

19665729 magnetic materials

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