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458 ⏐⏐⏐ MAGNETIC CIRCUITS
B � � � 0.352 T
Hglg � (7.96 � 10 5 )Bglg � (7.96 � 10 5 )(0.352 T)(0.001 m)
� 280.19 At
From the B-H curves,
Hcore � 850 At/m
Hcorelcore � (850 At/m)(0.16 m) � 136 At
Applying Ampère’s circuital law yields
NI � Hcorelcore � Hglg � 136 At � 280.19 At
NI � 416.19 At > 400 At (but within �5%
and therefore acceptable)
The solution is, therefore,
� � 1.057 � 10 �3 1.057 � 10
Wb
�3 �
Wb
� ��2
A 0.003 m
11.15 APPLICATIONS
Recording Systems
The most common application of magnetic material is probably in the
increasing number of recording instruments used every day in the office
and the home. For instance, the VHS tape and the 8-mm cassette of Fig.
11.42 are used almost daily by every family with a VCR or cassette
player. The basic recording process is not that difficult to understand
and will be described in detail in the section to follow on computer hard
disks.
��� ���
FIG. 11.42
Magnetic tape: (a) VHS and 8-mm cassette (Courtesy of Maxell Corporation of
America); (b) manufacturing process (Courtesy of Ampex Corporation).