What is a practical example of hysteresis?
2 Answers
Hysteresis is a phenomenon where the response of a system depends on its history, not just its current state. It is commonly observed in various physical systems and materials. A practical example of hysteresis is found in magnetic materials, such as iron, when exposed to a magnetic field.
### Example: Magnetic Hysteresis in Iron
1. **Application of Magnetic Field:**
- When an external magnetic field is applied to iron, the magnetic domains within the iron align with the field. This alignment increases the magnetic flux density (B) within the material.
2. **Removal of Magnetic Field:**
- After the external magnetic field is removed, the magnetic domains in the iron do not return to their original, random state immediately. Some of the alignment remains, resulting in a residual magnetization (the material remains magnetized to some extent).
3. **Hysteresis Loop:**
- If you plot the magnetic flux density (B) against the applied magnetic field (H), you get a looped curve known as the hysteresis loop. This loop shows that the magnetization of the material depends on the history of the applied field. Specifically, the magnetization increases with the applied field and decreases differently as the field is reduced, resulting in a loop.
### Key Points:
- **Magnetic Saturation:** The iron reaches a point where increasing the magnetic field further doesn't significantly increase magnetization. This is known as magnetic saturation.
- **Residual Magnetization:** Even after the external field is removed, the iron retains some magnetization. This is a result of the hysteresis effect.
- **Coercivity:** The amount of reverse magnetic field required to reduce the magnetization to zero is called coercivity. It indicates how resistant the material is to changes in its magnetization.
- **Energy Loss:** Hysteresis involves energy loss in the form of heat due to the continual realignment of magnetic domains. This is particularly important in transformers and electric motors, where hysteresis losses can affect efficiency.
This example illustrates how hysteresis manifests in a magnetic system and how the system's past states influence its current behavior.
### Example: Magnetic Hysteresis in Iron
1. **Application of Magnetic Field:**
- When an external magnetic field is applied to iron, the magnetic domains within the iron align with the field. This alignment increases the magnetic flux density (B) within the material.
2. **Removal of Magnetic Field:**
- After the external magnetic field is removed, the magnetic domains in the iron do not return to their original, random state immediately. Some of the alignment remains, resulting in a residual magnetization (the material remains magnetized to some extent).
3. **Hysteresis Loop:**
- If you plot the magnetic flux density (B) against the applied magnetic field (H), you get a looped curve known as the hysteresis loop. This loop shows that the magnetization of the material depends on the history of the applied field. Specifically, the magnetization increases with the applied field and decreases differently as the field is reduced, resulting in a loop.
### Key Points:
- **Magnetic Saturation:** The iron reaches a point where increasing the magnetic field further doesn't significantly increase magnetization. This is known as magnetic saturation.
- **Residual Magnetization:** Even after the external field is removed, the iron retains some magnetization. This is a result of the hysteresis effect.
- **Coercivity:** The amount of reverse magnetic field required to reduce the magnetization to zero is called coercivity. It indicates how resistant the material is to changes in its magnetization.
- **Energy Loss:** Hysteresis involves energy loss in the form of heat due to the continual realignment of magnetic domains. This is particularly important in transformers and electric motors, where hysteresis losses can affect efficiency.
This example illustrates how hysteresis manifests in a magnetic system and how the system's past states influence its current behavior.