A hysteresis loop is a device that has two “states” of operation. There are two different states, on and off, which are controlled by an electromechanical switch called the actuator. When the actuator moves from one state to another it takes time for this change in status to settle before returning back to its original position again.

The “hysteresis loop lung” is a medical condition that causes an individual to have different levels of blood pressure at different times. The issue can be treated by using the “hysteresis loop.”

The connection between the induced magnetic flux density and the magnetizing force is shown by the Hysteresis Loop, also known as the Hysteresis Curve or BH Curve. This article will cover what the Hysteresis Loop (BH Curve) is, its definition, the Magnetization Cycle, Hysteresis Loss, and how to minimize it.

## What is a Hysteresis Loop, and how does it work? – What is the BH Curve?

When a ferro-magnetic material like iron is exposed to a full cycle of magnetization, the phenomena of trailing of intensity of magnetization (I) or Magnetic Induction (B) behind the magnetizing field (H) is known as hysteresis.

**Introduction to the Hysteresis Loop (Fig. 1)**

When we insert an iron rod within a current carrying conductor, the conductor’s magnetic field causes the iron rod to acquire magnetic properties. The iron rod, on the other hand, becomes demagnetized when the current is reversed. This magnetization cycle is known as a Hysteresis Curve or Loop.

The BH Curve is a graph that depicts the relationship between two points depicts the relationship between the Magnetizing Force and the induced Magnetic Flux density (B) (H). In addition, as shown in Fig. 2, the shape of the BH Curve varies depending on the ferro-magnetic material. The magnetic characteristics of the material and its capacity to hold magnetization are determined by the form of the curve.

**BH Curves for (a) Iron that is pliable and (b) Hard Steel (Fig. 2)**

## Magnetization Cycle and Hysteresis: What’s the Connection?

Consider the case of an iron core in a solenoid, as illustrated in Fig. 3. When we increase the current via the solenoid, the magnetic intensity rises as well. This produced magnetic field is denoted by the letter H. When a consequence, as H grows, so does the magnetic flux density B. The curve OA of Hysteresis Loop in Fig. 4 illustrates this.

Through the solenoid, the current is raised even further. The value of the Magnetizing field rises at this moment, while the Magnetic flux density B remains same. As indicated in Fig. 4, this is known as point of saturation ‘A.’

**Figure 3: Solenoid with Iron Core**

### Retentivity Process

Now, we’ll lower the current in the solenoid until H = 0. De-magnetization of the iron begins here. Magnetic flux density continues and is not equal to ‘0’ even after the magnetizing field is ‘0’ or removed. This demonstrates that the iron core maintains some magnetization (OB), which we refer to as “Retentivity.”

### Coercivity Process

To eliminate the residual magnetization, we may change the direction of current via the solenoid such that H operates in the other way, as shown by the letter ‘OC.’ This reverse magnetizing field (OC) decreases the magnetizing field to ‘0,’ removing all magnetization from the material. This feature was formerly referred to as “coercivity.”

### The BH Curve

From here, we raise the current value even more, which increases the reverse magnetizing field. As a result, the value of B rises in the other direction until it reaches Saturation point ‘D’. Now, if the reverse magnetizing field is steadily reduced, the flux density will drop as well, as shown by the curve βDE’. At H = 0 and B 0 there is residual magnetization ‘OE’. We’ll use a forward magnetizing field, as shown by the curve EF, to eliminate the residual magnetization.

This whole loop is referred to as the “abcdefa” Cycle of Magnetization. In addition, the Magnetization Cycle demonstrates that Magnetic Induction follows behind the magnetizing force that produces it. This process is known as Hysteresis, and the resulting curve is known as the BH Curve or Hysteresis Loop.

**BH Curve or Hysteresis Loop (Fig. 4)**

## Definition of Hysteresis Loss

The energy needed to complete one full cycle of the BH Curve is known as Hysteresis Loss. The Magnetization Cycle expends energy that manifests as heat. Hyst. loss is the name given to this kind of heat loss. The area of the BH Curve shows the substance’s energy loss per unit volume.

The following is the equation for Hyst. Loss:

**Where,**

## How to Recover Hysteresis

We may successfully decrease losses by utilizing materials that have a high permeability and a low coercive force, such as:

- Soft Iron
- Alloys of Iron and Nickel
- Amorphous Magnetic Alloys are a kind of magnetic alloy that is amorphous in nature

## Hysteresis Loop Applications

Among the applications are:

- Because soft iron has a narrow BH Curve, it is often utilized in transformer cores.
- Hysteresis Loop for Steel has a big surface area, which is why it is used to make Permanent Magnets.
- The area of the BH Curve of various ferro-magnetic materials is used to choose materials for magnetic recording, memory devices, AC electrical equipment, and other applications.

## Hysthttp://memoryeresis Loop’s Benefits (BH Curve)

The benefits are as follows:

- The Hysteresis Loop is useful for calculating residual magnetism.
- A smaller loop area suggests less Hyst. loss.

## The BH Curve’s Drawbacks

The following are the drawbacks:

- The larger the loop’s size, the greater the Hysteresis Loss.
- With increasing frequency, this loss rises, resulting in lower output power efficiency.

Also see: Electromagnetic Induction: Theory, Applications, Benefits, and Drawbacks History, Theory, and Mathematical Expressions of the Hall Effect Principle Charging Stations for Electric Vehicles, Electric Vehicle Range

The “hysteresis loop formula” is a mathematical equation that describes the hysteresis loop. The equation goes like this: y = mx + b, where y is the output, x is the input, m is the slope of the line and b is the offset.

### Frequently Asked Questions

#### What causes hysteresis loop?

A: Hysteresis loops are caused by magnetic materials that have an iron or steel core. The energy used to magnetize the material is what causes the loop – so anything with a strong electromagnet can create these types of loops.

#### What is hysteresis in simple terms?

A: Hysteresis is a property of materials that causes them to be less elastic when they are strained and more resistant to further strain.

#### What is the hysteresis loop equation?

A: The hysteresis loop equation is a mathematical formula that describes the change in resistance as a function of time and temperature.

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