In electromagnetism, a magnetic circuit is an analogy to an electrical circuit, but instead of dealing with electric currents and voltages, it deals with magnetic flux and magnetomotive force (MMF). The relationship between these quantities is similar to Ohm's law in electrical circuits:
MMF
=
Flux
×
Reluctance
MMF=Flux×Reluctance
where MMF is the magnetomotive force (analogous to voltage), Flux is the magnetic flux (analogous to current), and Reluctance is the magnetic reluctance (analogous to resistance).
The magnetization curve (also known as the B-H curve) is a graphical representation of the relationship between magnetic flux density (
B) and magnetizing force (
H), or the relationship between magnetic induction and magnetizing current. This curve provides insights into how a material responds to an applied magnetic field, indicating its magnetic properties and behavior.
To determine the B-H or magnetization curve for a material, you can follow these steps:
Select a Sample Material: Choose the material for which you want to determine the B-H curve. This material could be a ferromagnetic material such as iron, steel, or any other material that exhibits magnetic properties.
Prepare the Setup: Set up a test apparatus that can generate a controlled magnetic field and measure the resulting magnetic flux density. This could involve using a solenoid coil with a known number of turns and applying a variable current to generate the magnetic field.
Measurements: Gradually increase the current passing through the coil in small increments while measuring the corresponding magnetic flux density using a magnetic flux density sensor (such as a Hall effect sensor or a magnetometer).
Plot the Data: With the measured data points (pairs of
B and
H), you can plot a graph of
B versus
H. The resulting curve is the magnetization curve or B-H curve for the material.
Interpretation: The shape of the curve reveals important characteristics of the material's magnetic behavior:
Initial Linear Region: At low magnetizing forces (
H), the material's response is approximately linear, resembling a straight line. This linear region is often used to define the material's permeability (
μ).
Saturation Region: As the magnetizing force increases, the material approaches a point where further increases in
H lead to relatively small changes in
B. This is known as magnetic saturation, and the material can no longer be magnetized significantly.
Hysteresis Loop: If you were to decrease the magnetizing force back to zero and then increase it in the opposite direction, the B-H curve wouldn't follow the same path. This difference between the ascending and descending curves is known as hysteresis, which is a property of the material's ability to retain magnetization even after the magnetic field is removed.
Analysis: Based on the shape of the curve, you can extract information about the material's magnetic properties, such as its saturation point, coercive force (the field required to demagnetize the material), and remanent flux density (the residual magnetic induction after the magnetic field is removed).
By determining the B-H curve, you gain valuable insights into how a material responds to magnetic fields, making it useful for designing magnetic components such as transformers, inductors, and electromagnets.