When it comes to ferrite, there is a lot of terminology that can be difficult to understand – especially if you have limited knowledge of the subject. In this blog we aim to break down some of the key terms you should know in order to have a good understanding of ferrite’s properties and behaviours.
Permeability (μ, mu)
Permeability is a measure of how easily a material can become magnetised. It tells us how well a material responds to the presence of a magnetic field.
Imagine permeability as the material’s magnetic sensitivity. High permeability means the material readily responds to a magnetic field, making it easier to magnetise. On the other hand, low permeability indicates resistance to magnetisation.
Unit of Measurement
Henrys per metre (H/m)
Initial Permeability (μi)
Initial Permeability refers to the permeability of a material when it is first subjected to a magnetic field. It indicates how easily the material responds to magnetisation under initial conditions.
Think of Initial Permeability as the starting point for magnetisation. It represents the material’s inherent magnetic responsiveness before any external factors influence its behaviour.
Amplitude Permeability (μa)
Amplitude Permeability is the maximum value of permeability reached by a material when exposed to a varying magnetic field, such as in alternating current (AC) applications.
Consider Amplitude Permeability as the peak responsiveness of the material to fluctuations in magnetic fields. It reflects how well the material can maintain magnetisation under varying conditions.
Coercivity (Hc)
Coercivity, also referred to as coercive field or coercive force, is the measure of a material’s resistance to becoming demagnetised. It represents the amount of reverse magnetic field needed to reduce the material’s magnetisation to zero.
Think of coercivity as the material’s stubbornness to lose its magnetisation. High coercivity implies it takes a significant effort to demagnetise the material, while low coercivity means the material easily loses its magnetisation.
Unit of Measurement
Amperes per metre (A/m)
Saturation (Bs)
Saturation is the point at which a material cannot be magnetised any further. Beyond this point, applying additional magnetic force doesn’t result in increased magnetisation.
It’s like trying to absorb more water with a sponge that’s already saturated – there’s a limit to how much it can hold.
Unit of Measurement
Tesla (T) or Gauss (G)
Curie Temperature (Tc)
Curie Temperature is the temperature at which a material undergoes a phase transition, causing a significant change in its magnetic properties. Above this temperature, the material loses its magnetic capabilities.
Consider Curie Temperature as the “heat threshold” for magnetism. When a material is heated beyond this point, its magnetic behaviour transforms and it loses its magnetisation.
Unit of Measurement
Degrees Celsius (°C) or Kelvin (K)
Magnetic Flux Density (B)
Magnetic Flux Density, often simply referred to as flux density, is a measure of the strength of a magnetic field. It quantifies the amount of magnetic flux passing through a given area.
Imagine Magnetic Flux Density as the concentration of magnetic field lines within a specified region. Higher flux density indicates a stronger magnetic field, while lower values signify a weaker field.
Unit of Measurement
Militesla (mT)
Core Losses (Pv)
Core Losses, also known as iron losses or magnetic losses, refer to the energy dissipated as heat within a magnetic core when subjected to alternating magnetic fields. These losses occur due to hysteresis and eddy currents.
Core Losses are a crucial consideration in transformer and inductor design, as they impact the efficiency and performance of magnetic components.
Unit of Measurement
Kilowatt per metre cubed (kW/m³)
Resistivity (ρ)
Resistivity is a measure of a material’s inherent opposition to the flow of electrical current. It indicates how effectively a material resists the passage of electrical charges.
Think of Resistivity as the material’s reluctance to allow the flow of electricity. Higher resistivity means greater opposition to current flow, while lower resistivity implies better conductivity.
Unit of Measurement
Ohm Metre (Ωm)
Understanding Ferrite’s Properties
Whether you’re starting a DIY project, studying engineering, or simply curious about the world of magnetism, these foundational concepts can help you to understand ferrite and its magnetic properties. Now that you have a basic understanding of what these terms mean, we can start to explore the different ferrite materials and forms that are available, along with how they can be beneficial for particular applications.
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