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Mehran University
Of Engineering & Technology,SZAB Khairpur Mirs Capus
ENGR. AHSANULLAH MEMON!ECTU"E"
#E$A"TME%T O E!ECT"'CA! E%('%EE"'%( MUCET K)A'"$U" M'"S
MAGNETIC HYSTERESIS
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Soe iportant ters
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HYSTERESIS LOOP't is *efine* as the lagging of agneti+ation or
flu *ensity -B.
/ehin* the agnetising force0't ay also /e *efine* as that
1uality of agnetic su/stance
*ue to 2hich energy is *essipate* in it on the reversal of
its
agnetis0
't is also calle* as B3) curve4hen an eternal agnetic fiel* is
applie* to a ferroagnet
such as iron, the atoic *ipoles align theselves 2ith it0Even
2hen the fiel* is reove*, part of the alignent 2ill /e
retaine*5 the aterial has /ecoe magnetized 0Once agneti+e*,
the agnet 2ill stay agneti+e* in*efinitely0To *eagneti+e it
re1uires heat or a agnetic fiel* in the
opposite *irection0
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The loop is generate* /y easuring the agnetic flu of a
ferroagnetic aterial 2hile the agneti+ing force is change*0A
ferroagnetic aterial that has never /een previously agneti+e*
or has /een thoroughly *eagneti+e* 2ill follo2 the *ashe* line
as H isincrease*0As the line *eonstrates, the greater the
aount of current applie*
(H+), the stronger the agnetic fiel* in the coponent (B+)0At
point 6a6 alost all of the agnetic *oains are aligne* an* an
a**itional increase in the agneti+ing force 2ill pro*uce very
littleincrease in agnetic flu0The aterial has reache* the point of
agnetic saturation0 4hen H is
re*uce* to +ero, the curve 2ill ove fro point 6a6 to point 6/06
At this
point, it can /e seen that soe agnetic flu reains in the
aterial
even though the agneti+ing force is +ero0This is referre* to as
the point of retentivity on the graph an* in*icates
the reanence or level of resi*ual agnetis in the aterial0 -Soe
of
the agnetic *oains reain aligne* /ut soe have lost their
alignent0.
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As the agneti+ing force is reverse*, the curve oves to point
6c6,
2here the flu has /een re*uce* to +ero0 This is calle* the point
of
coercivity on the curve0 -The reverse* agneti+ing force has
flippe*
enough of the *oains so that the net flu 2ithin the aterial
is+ero0.
The force re1uire* to reove the resi*ual agnetis fro the
aterial is calle* the coercive force or coercivity of the
aterial0
As the agneti+ing force is increase* in the negative *irection,
the
aterial 2ill again /ecoe agnetically saturate* /ut in the
opposite
*irection -point 6*6.0
"e*ucing H to +ero /rings the curve to point 6e06 't 2ill
have a level
of resi*ual agnetis e1ual to that achieve* in the other
*irection0
'ncreasing H /ac7 in the positive *irection 2ill return B
to +ero0 %otice that the curve *i* not return to the origin of
the graph /ecause
soe force is re1uire* to reove the resi*ual agnetis0 The
curve
2ill ta7e a *ifferent path fro point 6f6 /ac7 to the saturation
point
2here it 2ith coplete the loop0
