Which of the following statement related to the hysteresis loop is incorrect?

Options

A. The curve of B against H for a ferromagnetic material is called hysteresis loop
B. The area of B-H curve is a measure of power dissipated per cycle per unit, area of the specimen
C. Coactivity is a measure of the magnetic field required to destroy the residual magnetism of ferromagnetic material
D. The retentively of a speciment is the measure of magnetic field remaining in the speciment when the magnetising field is removed

Answer

To solve the question regarding the incorrect statement related to the hysteresis loop, we will analyze each statement based on our understanding of the B-H curve (magnetic flux density vs. magnetizing field).

### Step-by-Step Solution:

1. **Understanding the Hysteresis Loop**:
- The hysteresis loop is a graphical representation of the relationship between the magnetic flux density (B) and the magnetizing field (H) for a magnetic material. It shows how the material responds to an external magnetic field and how it retains magnetization.

2. **Identifying Key Terms**:
- **Retentivity**: This is the ability of a magnetic material to retain some magnetization after the external magnetizing field is removed. It corresponds to the value of B when H is zero.
- **Coercivity**: This is the measure of the magnetic field strength required to reduce the magnetization of a material to zero after it has been magnetized. It corresponds to the value of H when B is zero.

3. **Analyzing Each Statement**:
- **Statement A**: "The curve of B against H for a magnetic material is called the hysteresis loop."
- This statement is correct as it accurately describes the B-H curve.

- **Statement B**: "The area of the B-H loop is a measure of power dissipated per cycle per unit area of the specimen."
- This statement is incorrect. The area of the hysteresis loop represents the energy lost per cycle due to the magnetization and demagnetization process, not power. Power is the rate of energy loss, while the area represents total energy loss.

- **Statement C**: "Coercivity is a measure of the magnetic field required to destroy the residual magnetism in a ferromagnetic material."
- This statement is correct as it accurately describes coercivity.

- **Statement D**: "The retentivity of a sample is a measure of the magnetizing field remaining in the sample when the magnetizing field is removed."
- This statement is also correct as it describes retentivity accurately.

4. **Conclusion**:
- The only incorrect statement among the options provided is **Statement B**.

### Final Answer:
The incorrect statement related to the hysteresis loop is **Statement B**.

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