Magnetic Field Strength

The magnetic fields generated by currents and calculated from Ampere's Law or the Biot-Savart Law are characterized by the magnetic field B measured in Tesla. But when the generated fields pass through magnetic materials which themselves contribute internal magnetic fields, ambiguities can arise about what part of the field comes from the external currents and what comes from the material itself. It has been common practice to define another magnetic field quantity, usually called the "magnetic field strength" designated by H. It can be defined by the relationship

由电流产生的磁场以及通过安培定律或毕奥-萨伐尔定律计算出的磁场，其特征是用磁场B（单位为特斯拉）来表示。但是当这些产生的磁场穿过具有自身内部磁场的磁性材料时，关于磁场中哪部分来自外部电流、哪部分来自材料本身就会产生歧义。因此，人们通常定义另一个磁场量，通常称为“磁场强度”，用H表示。它可以由以下关系定义：

and has the value of unambiguously designating the driving magnetic influence from external currents in a material, independent of the material's magnetic response. The relationship for B can be written in the equivalent form

并能明确地标识出材料中由外部电流产生的驱动磁影响，无论材料的磁响应如何。B 的关系可以写成等效形式

H and M will have the same units, amperes/meter. To further distinguish B from H, B is sometimes called the magnetic flux density or the magnetic induction. The quantity M in these relationships is called the magnetization of the material.

H 和 M 的单位相同，都是安培/米。为了进一步区分 B 和 H，B 有时也被称为磁通量密度或磁感应强度。在这些关系中，M 这个量称为材料的磁化。

另一种常用的表示B与H之间关系的形式是

μ₀ being the magnetic permeability of space and K_m the relative permeability of the material. If the material does not respond to the external magnetic field by producing any magnetization, then K_m = 1. Another commonly used magnetic quantity is the magnetic susceptibility which specifies how much the relative permeability differs from one.

μ₀ 是空间的磁导率，K_m 是材料的相对磁导率。如果材料不对外磁场产生任何磁化，则 K_m = 1。另一个常用的磁量是磁化率，它说明相对磁导率与 1 的差异程度。

For paramagnetic and diamagnetic materials the relative permeability is very close to 1 and the magnetic susceptibility very close to zero. For ferromagnetic materials, these quantities may be very large.

对于顺磁性和抗磁性材料，相对磁导率非常接近1，磁化率也非常接近零。而对于铁磁性材料，这些量可能非常大。

The unit for the magnetic field strength H can be derived from its relationship to the magnetic field B, B=μH. Since the unit of magnetic permeability μ is N/A², then the unit for the magnetic field strength is:

磁场强度H的单位可以从它与磁场B的关系导出，B=μH。由于磁导率μ的单位是N/A²，因此磁场强度的单位是：

An older unit for magnetic field strength is the oersted: 1 A/m = 0.01257 oersted

一种较旧的磁场强度单位是奥斯特：1 A/m = 0.01257 奥斯特

H = B/μ m = B/μ 0 - M B = μ 0 (H + M) B = μ m H μ = μ m = K m μ 0 Magnetic susceptibility χ m = K m - 1 T/(N/A 2 ) = (N/Am)/(N/A 2 ) = A/m（专名或术语）

Magnetic Field Strength H