Question

What is the principle of hysteresis loss?

Answer 1

Hysteresis loss occurs in magnetic materials, like iron, when they are subjected to a changing magnetic field. The basic principle behind it is related to the way the magnetic domains in the material behave when the external magnetic field is altered.

Here's how it works:

1. Magnetic Domains: Inside ferromagnetic materials (like iron), there are tiny regions called magnetic domains, where the magnetic moments of atoms are aligned in the same direction. These domains can be reoriented by an external magnetic field.
   

1. Magnetization Process: When a magnetic field is applied to the material, these domains align with the external field, making the material magnetized. As the strength of the magnetic field increases, more domains align, and the material becomes more magnetized.
   

1. Reverse Field: When the external magnetic field is reduced, the domains don’t return immediately to their original disordered state. Some domains stay aligned even when the external field decreases, leading to a lag between the change in the magnetic field and the resulting magnetization of the material.
   

1. Hysteresis Loop: This behavior creates a loop when you plot magnetization (or flux density) against the applied magnetic field strength. This loop is called the hysteresis loop. It shows that the material's magnetization depends not just on the current field but also on its past history.
   

1. Energy Loss: As the magnetic field is cycled, some energy is lost in the form of heat due to the continuous realignment of magnetic domains. This loss is called hysteresis loss.
   

Key Points:

1. Hysteresis loss occurs because the magnetic material retains some magnetization even after the external field is removed or reversed.
   

1. This loss is proportional to the area of the hysteresis loop.
   

1. Materials with large hysteresis loops tend to have higher energy losses.
   

In practical applications, like transformers or electric motors, hysteresis loss contributes to inefficiency, which is why materials with low hysteresis loss (like silicon steel) are often used to reduce energy waste.