Pacific Scientific 5170, Инструкция по эксплуатации

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Section 1
Introduction
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 1-1.
One line of flux in the CGS measurement system is called a
maxwell (M) , but the weber (W), which is 108 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 area. The more commonly used
term is the tesla (T) , which is 10,000 lines per cm . 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 (Am) 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. Magnetic field strength deals with the
physical characteristics of magnetic materials whereas flux density does not. The only time the two are considered equal is in free space
(air). Only in free space is the following relationship true:
1 G = 1 Oe = 0.0001 T = 79.6 Am
Figure 1-1
Flux Lines of a Permanent Magnet
1-1