To obtain B-H curve of a magnetic materials.

Experiment Number: 08

AIM OF THE EXPERIMENT : –

                    To obtain B-H curve of a magnetic materials.

APPARATUS REQUIRED: –

CIRCUIT DIAGRAM: –

THEORY: –

When a Magneto motive force is applied to a homogeneous iron ring or core, a magnetic potential gradient is produced within the material and i.e expressed by H= (N*I)/l (where, H is magnetic field intensity or magnetic field strength, N is the number of turns of coil, I is the current supplied and l is the mean length of core).

from the above expression we may write H ∝ I ………… (i)

as l and N are constant quantity.

From faraday’s law of magnetic induction, we can write, induced emf (e) = – N*(dɸ/dt)…… (ii)

Since the supplied voltage is sinusoidal, the core flux is given by ɸ = ɸ_msin 𝛚t and substituting the value in equation (ii) , we may get

The above expression may be written as E_rms ∝ B_max ….. (iii)

Thus a graph of V-I can be drawn by taking the respective data of V and I.

This curve is similar to B-H curve.

PROCEDURES: –

1. All Instruments are connected as per circuit diagram shown in fig.
2. The voltage is increased gradually by single phase auto- transformer & corresponding readings of Voltmeters & Ammeters are filled in observation table.
3. Draw a graph of V₂ and I which will show the relation between B and H parameters.

PRECAUTIONS: –

1. Don’t switch on power supply without concerning teacher.
2. Single phase autotransformer must be kept at minimum potential point before switch on the experiment.

OBSERVATION TABLE: –

CONCLUSION:-

To be written by student.

For Your Reference: –

The B-H curve, also known as the magnetization curve or hysteresis loop, is a graphical representation of the relationship between the magnetic flux density (B) and the magnetic field strength (H) in a magnetic material. It illustrates how the material responds to an applied magnetic field.

Here’s a breakdown of the B-H curve:

1. Magnetization Process: When an external magnetic field is applied to a material, it causes the magnetic domains within the material to align with the field, resulting in magnetization. This process is represented by the initial curve of the B-H graph.
2. Saturation: As the external magnetic field strength (H) increases, the magnetic flux density (B) also increases until it reaches a point called saturation. At saturation, further increases in the magnetic field strength do not result in significant increases in magnetic flux density because most of the magnetic domains are already aligned.
3. Hysteresis: When the external magnetic field is reduced back to zero, the magnetic flux density does not return to zero. Instead, it follows a different path, creating a closed loop on the B-H graph. This phenomenon is known as hysteresis and is caused by the residual magnetization within the material.
4. Remanence: The magnetic flux density remaining in the material after the external magnetic field is removed is called remanence (Br). It is the point on the B-H curve where the magnetic field strength is zero but there is still a nonzero magnetic flux density.
5. Coercivity: The amount of reverse magnetic field strength (H) required to reduce the magnetic flux density (B) to zero is called coercivity (Hc). It represents the material’s resistance to demagnetization.
6. Energy Loss: The area inside the hysteresis loop represents the energy loss in the material due to magnetic hysteresis during each magnetization cycle.

Understanding the B-H curve is essential in designing magnetic components and devices, such as transformers, inductors, and electric motors, as it provides insight into the magnetic properties and behaviors of different materials.

Viva-voce Questions: –

1. What does the B-H curve represent ?

Answer: The B-H curve, also known as the magnetization curve or hysteresis loop, represents the relationship between the magnetic flux density (B) and the magnetic field strength (H) in a magnetic material.

2. What is the significance of the B-H curve ?

Answer: The B-H curve provides insights into the magnetic properties and behaviors of materials, including saturation magnetization, hysteresis, remanence, and coercivity. It is crucial for designing magnetic components and devices.

3. Describe the magnetization process as shown by the B-H curve.

Answer: Initially, as the external magnetic field strength (H) increases, the magnetic flux density (B) also increases until it reaches saturation. This represents the alignment of magnetic domains within the material.

4. What is saturation in the context of the B-H curve ?

Answer: Saturation occurs when further increases in the external magnetic field strength do not result in significant increases in magnetic flux density because most of the magnetic domains are already aligned.

5. Explain the phenomenon of hysteresis in the B-H curve.

Answer: Hysteresis is the phenomenon where the magnetic flux density (B) does not return to zero when the external magnetic field (H) is reduced to zero. Instead, it follows a different path, forming a closed loop on the B-H graph.

6. What is remanence ?

Answer: Remanence (Br) is the magnetic flux density remaining in the material after the external magnetic field is removed. It is the point on the B-H curve where the magnetic field strength is zero but there is still a nonzero magnetic flux density.

7. Define coercivity.

Answer: Coercivity (Hc) is the amount of reverse magnetic field strength required to reduce the magnetic flux density to zero. It represents the material’s resistance to demagnetization.

8. How is energy loss represented on the B-H curve ?

Answer: The area inside the hysteresis loop represents the energy loss in the material due to magnetic hysteresis during each magnetization cycle.

9. What are some applications where understanding the B-H curve is important ?

Answer: Understanding the B-H curve is crucial in designing magnetic components and devices such as transformers, inductors, electric motors, magnetic recording media, and magnetic sensors. It helps in selecting appropriate materials and optimizing their performance.