What Is coercivity and retentivity?

Answer:

Hysteresis loop provides a substance with the importance of retentivity and coercivity. Therefore the way to select the right material to make a permanent magnet is made simpler by the heart of machines. When a ferromagnetic material is magnetized by applying the external magnetizing field, after magnetization if we remove the external magnetizing field the material will not relax back to its zero magnetization position.

Coercivity

The amount of reverse(-ve H) external magnetizing field required to completely demagnetize the substance is known as coercivity of substance.

• Coercivity is defined as the minimum value of magnetising intensity that is required to bring the material to its original state.
• In the case of a ferromagnetic substance, when the applied magnetic field is increased in the reverse direction, then at some point H_c the substance completely loses its magnetization. This point is known as coercivity.

Retentivity

The ability of the magnetic field remaining in the material even after removing the external source is known as Retentivity.

• It tells us about the magnetic strength of the material.
• In other words when the applied magnetic field is decreased to zero after meeting the saturation point of magnetization, then the remaining magnetization shown by the substance is known as retentivity.

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1. What are paramagnetic substances?
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