F.W. Bell 7030, Инструкция по эксплуатации

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F.W. BELL Model 7030 Gauss/Tesla Meter Instruction Manual
Appendix A – Understanding Flux Density A-1
Appendix A Understanding Flux Density
Magnetic fields surrounding permanent magnets or electrical conductors can be visualized as a
collection of magnetic
flux lines; lines of force existing in the material that is being subjected to a
magnetizing influence. Unlike light, which travels away from its source indefinitely, magnetic flux
lines must eventually return to the source. Thus all magnetic sources are said to have two
poles .
Flux lines are said to emanate from the “north” pole and return to the “south” pole, as depicted in
Figure A-1 .
Figure A-1 Flux Lines of a Permanent Magnet
One line of flux in the cgs measurement system is called a
maxwell (Mx) , but the weber (Wb),
which is 10
8
lines, is more commonly used.
Flux density, also called magnetic induction, is the number of flux lines passing through a given
area. It is commonly assigned the symbol “
B ” in scientific documents. In the cgs system a gauss
(G) is one line of flux passing through a 1 cm
2
area. The more commonly used term is the tesla (T) ,
which is 10,000 lines per cm
2
. Thus
1 tesla = 10,000 gauss
1 gauss = 0.0001 tesla
Magnetic field strength is a measure of force produced by an electric current or a permanent
magnet. It is the ability to induce a magnetic field “
B ”. It is commonly assigned the symbol “ H ” in
scientific documents. The unit of “ H ” in the cgs system is an oersted (Oe), but the ampere/meter
(A/m) is more commonly used. The relationship is
1 oersted = 79.6 ampere/meter
1 ampere/meter = 0.01256 oersted
It is important to know that magnetic field strength and magnetic flux density are not the same. The
only time the two are considered equal is in free space. Only in free space is the following
relationship true:
1 G = 1 Oe = 0.0001 T = 79.6 A/m