What is b and h in A hysteresis loop?
2 Answers
In a hysteresis loop, **B** and **H** refer to magnetic flux density and magnetic field strength, respectively.
- **B (Magnetic Flux Density)**: It represents the amount of magnetic field passing through a given area. It is measured in teslas (T).
- **H (Magnetic Field Strength)**: This is the intensity of the magnetic field generated by an external source, measured in amperes per meter (A/m).
The hysteresis loop itself illustrates how a material's magnetization changes as the magnetic field is cycled, showing the relationship between B and H. The area within the loop represents energy loss due to hysteresis, which is important in applications like transformers and magnetic storage.
- **B (Magnetic Flux Density)**: It represents the amount of magnetic field passing through a given area. It is measured in teslas (T).
- **H (Magnetic Field Strength)**: This is the intensity of the magnetic field generated by an external source, measured in amperes per meter (A/m).
The hysteresis loop itself illustrates how a material's magnetization changes as the magnetic field is cycled, showing the relationship between B and H. The area within the loop represents energy loss due to hysteresis, which is important in applications like transformers and magnetic storage.
The hysteresis loop is a key concept in the study of magnetic materials and their magnetic properties. It describes how the magnetic state of a material changes as the external magnetic field is varied. Let's break down the terms \( B \) and \( H \) in this context:
### 1. Magnetic Field Strength (\( H \))
- **Definition**: \( H \), often referred to as the magnetic field strength or magnetizing force, represents the intensity of the external magnetic field applied to a material. It is a measure of how strong the magnetic field is in a given region.
- **Units**: It is typically measured in amperes per meter (A/m) in the International System of Units (SI).
### 2. Magnetic Flux Density (\( B \))
- **Definition**: \( B \), also known as magnetic flux density or magnetic induction, represents the amount of magnetic flux passing through a unit area perpendicular to the magnetic field. It indicates how much magnetic field is present in the material.
- **Units**: It is measured in teslas (T) in SI units. One tesla is equal to one weber per square meter (Wb/m²).
### Hysteresis Loop Overview
The hysteresis loop is a graphical representation of how \( B \) (magnetic flux density) responds to changes in \( H \) (magnetic field strength). Here's how the loop is typically depicted and what it represents:
1. **Initial Magnetization Curve**:
- When an unmagnetized material is exposed to an increasing magnetic field \( H \), the magnetic flux density \( B \) initially rises slowly as the magnetic domains align with the field. This part of the curve shows the initial magnetization of the material.
2. **Saturation**:
- As \( H \) increases further, \( B \) eventually levels off, reaching a maximum value called the saturation magnetization. At this point, most of the magnetic domains are aligned, and increasing \( H \) won't significantly increase \( B \).
3. **Reduction of \( H \) and Remanence**:
- If \( H \) is then decreased back to zero, \( B \) doesn’t return to zero immediately but retains a certain level of magnetization, known as the remanent magnetization (\( B_r \)). This indicates that the material has been magnetized and retains some magnetic flux density even when the external field is removed.
4. **Negative Saturation and Coercivity**:
- Continuing to decrease \( H \) will eventually cause \( B \) to become negative as the magnetic domains realign in the opposite direction. This negative saturation occurs when the material is fully magnetized in the opposite direction.
5. **Return to Original State**:
- If \( H \) is then reversed and increased back to its original positive value, the curve retraces a different path compared to the initial magnetization curve. This path forms a closed loop, demonstrating hysteresis, which is the dependence of the state of the material on its history of magnetization.
6. **Coercivity**:
- The coercivity (\( H_c \)) is the measure of the material's resistance to becoming demagnetized. It is the value of \( H \) required to reduce the magnetic flux density \( B \) to zero after reaching saturation in the opposite direction.
7. **Loop Area**:
- The area within the hysteresis loop represents the energy loss per cycle of magnetization and demagnetization, which is important in applications like transformers and magnetic memory devices.
### Summary
- **\( H \) (Magnetic Field Strength)**: The external field applied to the material.
- **\( B \) (Magnetic Flux Density)**: The response of the material to the external field, showing the degree of magnetization.
The hysteresis loop effectively demonstrates how the material’s magnetic properties depend on its history of exposure to magnetic fields and highlights key characteristics like saturation, remanence, and coercivity.
### 1. Magnetic Field Strength (\( H \))
- **Definition**: \( H \), often referred to as the magnetic field strength or magnetizing force, represents the intensity of the external magnetic field applied to a material. It is a measure of how strong the magnetic field is in a given region.
- **Units**: It is typically measured in amperes per meter (A/m) in the International System of Units (SI).
### 2. Magnetic Flux Density (\( B \))
- **Definition**: \( B \), also known as magnetic flux density or magnetic induction, represents the amount of magnetic flux passing through a unit area perpendicular to the magnetic field. It indicates how much magnetic field is present in the material.
- **Units**: It is measured in teslas (T) in SI units. One tesla is equal to one weber per square meter (Wb/m²).
### Hysteresis Loop Overview
The hysteresis loop is a graphical representation of how \( B \) (magnetic flux density) responds to changes in \( H \) (magnetic field strength). Here's how the loop is typically depicted and what it represents:
1. **Initial Magnetization Curve**:
- When an unmagnetized material is exposed to an increasing magnetic field \( H \), the magnetic flux density \( B \) initially rises slowly as the magnetic domains align with the field. This part of the curve shows the initial magnetization of the material.
2. **Saturation**:
- As \( H \) increases further, \( B \) eventually levels off, reaching a maximum value called the saturation magnetization. At this point, most of the magnetic domains are aligned, and increasing \( H \) won't significantly increase \( B \).
3. **Reduction of \( H \) and Remanence**:
- If \( H \) is then decreased back to zero, \( B \) doesn’t return to zero immediately but retains a certain level of magnetization, known as the remanent magnetization (\( B_r \)). This indicates that the material has been magnetized and retains some magnetic flux density even when the external field is removed.
4. **Negative Saturation and Coercivity**:
- Continuing to decrease \( H \) will eventually cause \( B \) to become negative as the magnetic domains realign in the opposite direction. This negative saturation occurs when the material is fully magnetized in the opposite direction.
5. **Return to Original State**:
- If \( H \) is then reversed and increased back to its original positive value, the curve retraces a different path compared to the initial magnetization curve. This path forms a closed loop, demonstrating hysteresis, which is the dependence of the state of the material on its history of magnetization.
6. **Coercivity**:
- The coercivity (\( H_c \)) is the measure of the material's resistance to becoming demagnetized. It is the value of \( H \) required to reduce the magnetic flux density \( B \) to zero after reaching saturation in the opposite direction.
7. **Loop Area**:
- The area within the hysteresis loop represents the energy loss per cycle of magnetization and demagnetization, which is important in applications like transformers and magnetic memory devices.
### Summary
- **\( H \) (Magnetic Field Strength)**: The external field applied to the material.
- **\( B \) (Magnetic Flux Density)**: The response of the material to the external field, showing the degree of magnetization.
The hysteresis loop effectively demonstrates how the material’s magnetic properties depend on its history of exposure to magnetic fields and highlights key characteristics like saturation, remanence, and coercivity.