Coercivity formula

Explore the coercivity formula, its significance in magnetic materials, factors affecting it, and an example calculation.

Understanding the Coercivity Formula

Coercivity is a fundamental property of magnetic materials, representing the intensity of the magnetic field required to reduce the magnetization of the material to zero after it has been magnetized to saturation. In this article, we will explore the coercivity formula and its significance in the study of magnetic materials.

Basic Concepts

Before diving into the coercivity formula, it is essential to understand some basic concepts:

• Magnetization (M): The measure of the magnetic moment per unit volume of a material.
• Magnetic Field (H): A vector field surrounding a magnet, generated by the motion of electric charges.
• Coercivity (H_c): The intensity of the magnetic field required to demagnetize a magnetic material after being saturated.

The Coercivity Formula

The coercivity formula is derived from the magnetization curve, also known as the B-H curve, which is a plot of the magnetic flux density (B) against the magnetic field (H). The coercivity is the value of the magnetic field (H) at the point where the magnetization (M) becomes zero on the B-H curve. Mathematically, it can be represented as:

H_c = H(M = 0)

Significance of Coercivity

Coercivity is a crucial property that helps in classifying magnetic materials and determining their applications:

1. Hard Magnetic Materials: These materials have high coercivity, meaning they require a strong magnetic field to be demagnetized. They can maintain their magnetization for a long time, making them ideal for permanent magnets used in various applications like electric motors, generators, and hard disk drives.
2. Soft Magnetic Materials: Materials with low coercivity are easily demagnetized and magnetized. These materials are suitable for applications where the magnetic field needs to change frequently, such as transformers, inductors, and magnetic shielding.

Factors Affecting Coercivity

Coercivity is influenced by several factors, such as:

• Material Composition: The type of elements and their arrangement in the material can significantly affect its coercivity.
• Grain Size: Smaller grain sizes usually result in higher coercivity, as the magnetic domains are more challenging to reorient.
• Temperature: Coercivity generally decreases with an increase in temperature due to the increased thermal energy, which can easily reorient the magnetic domains.

In conclusion, the coercivity formula is a vital concept in understanding the behavior and properties of magnetic materials. Its value has a significant impact on the material’s applications and performance in various industries.

Example of Coercivity Calculation

Let’s consider a hypothetical magnetic material with the following data points obtained from its B-H curve:

• (H₁, M₁) = (-500 Oe, 1000 emu/cm³)
• (H₂, M₂) = (-400 Oe, 400 emu/cm³)
• (H₃, M₃) = (-300 Oe, 0 emu/cm³)

According to the coercivity formula, we need to find the value of the magnetic field (H) when the magnetization (M) becomes zero. From the data points above, we can see that the coercivity is:

H_c = H(M = 0) = -300 Oe

In this example, the coercivity of the magnetic material is -300 Oe. The negative sign indicates that the magnetic field is applied in the opposite direction to the initial magnetization. This value of coercivity can help us determine if the material is suitable for specific applications, such as permanent magnets or transformer cores.