In electromagnetism, the relationship between magnetic flux density (B) and magnetic field strength (H) is described by the concept of a magnetic circuit. This concept is analogous to the way electric circuits are used to understand the relationship between voltage, current, and resistance in electrical systems. Let's delve into the details:
Magnetic Flux Density (B): Magnetic flux density, often referred to simply as "magnetic field" or "magnetic induction," is denoted by the symbol B. It represents the strength of the magnetic field at a specific point in space. The unit of magnetic flux density is the tesla (T).
Magnetic Field Strength (H): Magnetic field strength, denoted by H, is a measure of the intensity of the magnetic field within a material. It's similar to the concept of electric field strength in electric circuits. The unit of magnetic field strength is ampere per meter (A/m).
The relationship between B and H is similar to the relationship between voltage (V) and current (I) in an electrical circuit. In an electric circuit, Ohm's law (V = IR) relates voltage, current, and resistance. In a magnetic circuit, the relationship between B, H, and the material properties is defined by the magnetic analog of Ohm's law, called the magnetic flux density law:
B = μ₀ * (H + M)
Where:
B is the magnetic flux density (in teslas, T).
H is the magnetic field strength (in amperes per meter, A/m).
M is the magnetization of the material (in amperes per meter, A/m).
μ₀ (mu naught) is the permeability of free space, a constant with a value of approximately 4π × 10^-7 T·m/A.
The term (H + M) represents the total magnetizing field within a material. H represents the externally applied field, and M represents the internal magnetization of the material due to the alignment of its atomic or molecular magnetic moments.
This relationship helps us understand how the presence of materials with different magnetic properties affects the behavior of magnetic fields. Materials with higher magnetization (M) will contribute more to the total magnetic field (B) for a given applied magnetic field (H).
In summary, the relationship between magnetic flux density (B) and magnetic field strength (H) in a magnetic circuit is described by the magnetic flux density law, which takes into account the applied field (H) and the internal magnetization of the material (M).