# How hysteresis works in physics

Learn about hysteresis in physics, a phenomenon where a system’s response lags behind changes in external conditions. Explore its types and applications.

## Understanding Hysteresis in Physics

Hysteresis is a phenomenon that occurs in various physical systems. It refers to the lag or delay in the response of a system to changes in the forces or fields acting upon it. This effect is caused by the system’s internal memory, which retains some of its previous states, even after the external conditions have changed. In this article, we will explore how hysteresis works in physics and some of its applications.

## How Hysteresis Works

Hysteresis occurs in physical systems that have a memory or history-dependent response. The most common example of hysteresis is seen in ferromagnetic materials. When these materials are exposed to an external magnetic field, they become magnetized in the same direction as the field. However, when the field is removed, the material retains some of its magnetization. This means that the magnetic response of the material lags behind the applied field, resulting in hysteresis.

The reason behind this phenomenon is the existence of domains within the material that are oriented in different directions. These domains represent regions of the material where the magnetic moments are aligned in a particular direction. When a magnetic field is applied, the domains start to align with the field, resulting in the overall magnetization of the material. However, when the field is removed, the domains do not return to their initial orientation, resulting in the retention of some magnetization. The material will only lose its magnetization when the applied field reaches a certain critical value, known as the coercive field.

Hysteresis can also be observed in other physical systems, such as the behavior of elastic materials. When a force is applied to an elastic material, it deforms in response. However, when the force is removed, the material does not return to its original shape immediately. This is because the deformation causes changes in the material’s structure, which require some time to relax back to their initial state. This effect is known as mechanical hysteresis and is observed in materials such as rubber, where it is responsible for the material’s elasticity.

## Applications of Hysteresis

Hysteresis has several practical applications in physics and engineering. One such application is in the design of magnetic switches and relays. These devices use the hysteresis of ferromagnetic materials to control the flow of electrical current. When a magnetic field is applied to the material, it becomes magnetized and can attract or repel nearby magnetic objects. This effect is used to control the position of a switch or relay, allowing for the precise control of electrical circuits.

Another application of hysteresis is in the design of thermostats and other temperature control systems. These devices use the hysteresis of materials such as bimetallic strips to control the temperature. When the temperature rises above a certain threshold, the material expands, causing the switch to turn off the heating element. However, the material does not contract immediately when the temperature drops, resulting in a delay before the switch turns on the heating element again. This delay helps to prevent rapid temperature fluctuations, resulting in a more stable temperature control system.

In conclusion, hysteresis is a fascinating phenomenon that occurs in various physical systems. It is caused by the internal memory of the system, which retains some of its previous states, even after the external conditions have changed. This effect has several practical applications in physics and engineering, such as in the design of magnetic switches, relays, and temperature control systems. Understanding hysteresis is essential for developing new technologies and improving existing ones.

## Types of Hysteresis

There are different types of hysteresis that occur in various physical systems, including ferromagnetic hysteresis, elastic hysteresis, electrical hysteresis, and optical hysteresis. In ferromagnetic hysteresis, the magnetization of the material lags behind the applied magnetic field. Elastic hysteresis is observed in materials such as rubber and occurs when the material does not return to its initial shape immediately after the applied force is removed. Electrical hysteresis is observed in materials such as capacitors and occurs when the electric polarization of the material lags behind the applied electric field. Optical hysteresis is observed in materials such as liquid crystals and occurs when the optical response of the material lags behind the applied light intensity.

## Conclusion

In conclusion, hysteresis is a fascinating phenomenon that occurs in various physical systems. It is caused by the internal memory of the system, which retains some of its previous states, even after the external conditions have changed. Understanding hysteresis is crucial for developing new technologies and improving existing ones. It has several practical applications in physics and engineering, such as in the design of magnetic switches, relays, and temperature control systems. Hysteresis occurs in different forms in various physical systems, including ferromagnetic hysteresis, elastic hysteresis, electrical hysteresis, and optical hysteresis. Each type of hysteresis has its unique characteristics and applications, making it a fascinating area of study in physics.