Dr Sushil Kumar
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Best-known Magnetic Susceptibility Experiment 20 Viva Questions
Last updated on Tuesday, February 28th, 2023
Viva Questions:
How to determine magnetic susceptibility using FeCl3 liquid in Quincke’s tube experiment. Some viva questions are listed here that might be useful for you to understand the experiment. I have not written the answer here because if you have performed the experiment it is obvious you will be familiar with these answers. If by chance you don’t get an answer directly from any source you can ask by comment box.
Experiment Related Information:
Personally I feel the viva questions provide a vision to understand the physical concept with a new vision. What happens in the lab? We just note down the reading and then calculations etc, but rarely some students analyze the results.
These questions actually help to develop that analysis part. Hope it will help you.
1. What is susceptibility?
Susceptibility is a physical property of a material that describes its ability to become magnetized in the presence of an external magnetic field. It is a dimensionless quantity that represents the ratio of the induced magnetization of a material to the strength of the magnetic field that produced it. In other words, susceptibility quantifies how easily a material can be magnetized.
2. What is magnetization and how it can be achieved?
Magnetization is the process by which a material is magnetized, i.e., it develops a magnetic moment and becomes magnetic. This can be achieved in several ways, including:
By exposing the material to an external magnetic field
By passing an electric current through the material: Some materials, such as iron, nickel, and cobalt, can be magnetized by passing an electric current through them. This is known as the electromagnet effect and is the principle behind the operation of electric motors, generators, and transformers.
By heating the material above its Curie temperature: Some materials, such as iron, lose their magnetization when heated above a certain temperature, known as the Curie temperature. When such materials are cooled back down below the Curie temperature in the presence of an external magnetic field, they become magnetized.
By rubbing the material with a magnet: This is a simple way to magnetize a material, known as the rubbing or stroking method. When a magnet is rubbed against a magnetic material, it aligns the magnetic moments within the material, causing it to become magnetized.
3. Does an atom with one electron in the outer shell can behave like a bar magnet? or simply do an atom can be equivalent to the bar magnet?
Yes, magnetic moment of an electron in an atom
4. What is the atomic dipole?
Watch this video to make this concept more clear
5. How to find the atomic dipole element?
Explain in the above video
6. What is magnetic field induction and magnetic field intensity, how you will define it and what is the relationship between them?
Magnetic field induction, also known as magnetic flux density.
Magnetic field intensity, also known as magnetic field strength, is a measure of the magnetic field produced by a current-carrying wire or a magnet. It is defined as the force per unit length per unit current acting on a wire that is placed parallel to the magnetic field.
The relationship between magnetic field induction and magnetic field intensity is given by the equation:
B = μ₀H
where B is the magnetic field induction in tesla (T), H is the magnetic field intensity in amperes per meter (A/m), and μ₀ is the permeability of free space, which has a value of 4π × 10⁻⁷ N/A².
7. How do you see magnetic field density in a region of a magnetic field by bar magnet?
Through the magnetic field lines of forces
8. What is the unit of magnetic field induction (density) and magnetic field intensity and from which letters we represent to them?
B is the magnetic field induction in tesla (T), H is the magnetic field intensity in amperes per meter (A/m), and μ₀ is the permeability of free space, which has a value of 4π × 10⁻⁷ N/A².
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9. What is the role of an external magnetic field in the magnetization of the material, how atomic dipole moments of atoms play the role in the magnetization?
The external magnetic field plays a crucial role in the magnetization of a material. When a material is placed in an external magnetic field, the field exerts a force on the magnetic dipole moments of the atoms in the material. The dipole moments align themselves with the direction of the external magnetic field. This alignment of magnetic dipole moments creates a net magnetic moment in the material, which is known as magnetization.
The atomic dipole moments of the atoms in the material are responsible for the magnetization of the material. Each atom has its own magnetic dipole moment, which arises from the orbital and spin motion of electrons around the nucleus. In the absence of an external magnetic field, the magnetic dipole moments of the atoms in the material are randomly oriented, resulting in zero net magnetization.
However, in the presence of an external magnetic field, the magnetic dipole moments of the atoms experience a torque, which causes them to align with the direction of the field. As more and more atomic dipoles align with the external magnetic field, the material becomes more magnetized.
10. Can you explain the types of magnetic material (Diamagnetic, Paramagnetic, Ferromagnetic, Antiferromagnetic) on the basis of atomic dipole moments?
The magnetic behavior of a material depends on the atomic dipole moments of the atoms in the material. Based on their magnetic properties, materials can be classified into four main categories: diamagnetic, paramagnetic, ferromagnetic, and antiferromagnetic.
Diamagnetic Materials:
Diamagnetic materials have atoms with no unpaired electrons, and therefore, they have no net magnetic moment. When placed in an external magnetic field, the atomic dipoles align themselves in such a way as to create a magnetic field that opposes the external field, resulting in a slight decrease in the overall magnetic field. Diamagnetic materials have a negative magnetic susceptibility, which means that they are slightly repelled by a magnetic field. Examples of diamagnetic materials include copper, silver, gold, and zinc.
Paramagnetic Materials:
Paramagnetic materials have atoms with unpaired electrons, and therefore, they have a net magnetic moment. When placed in an external magnetic field, the atomic dipoles align themselves with the external field, resulting in an increase in the overall magnetic field. Paramagnetic materials have a positive magnetic susceptibility, which means that they are weakly attracted to a magnetic field. Examples of paramagnetic materials include aluminum, platinum, and tungsten.
Ferromagnetic Materials:
Ferromagnetic materials also have atoms with unpaired electrons, and their magnetic moments are strongly coupled with each other due to interactions between the atoms. This coupling results in a strong net magnetic moment for the material, even in the absence of an external magnetic field. When placed in an external magnetic field, the atomic dipoles align themselves with the external field, resulting in an even stronger magnetization. Ferromagnetic materials have a high positive magnetic susceptibility, which means that they are strongly attracted to a magnetic field. Examples of ferromagnetic materials include iron, cobalt, and nickel.
Antiferromagnetic Materials:
Antiferromagnetic materials have atoms with unpaired electrons, but their magnetic moments are oriented in such a way that they cancel each other out, resulting in zero net magnetic moment for the material in the absence of an external magnetic field. When placed in an external magnetic field, the atomic dipoles try to align themselves with the external field, but they are offset by neighboring dipoles that are trying to align themselves in the opposite direction. As a result, antiferromagnetic materials exhibit a weak magnetic response to an external magnetic field. Examples of antiferromagnetic materials include manganese oxide and chromium.
11. In which unit you measure the magnetic field intensity H, meniscus height h in your observation?
H is the magnetic field intensity in amperes per meter (A/m), in mm, that can be converted further in meter
12. Do you have plot the graph between h and H^2, if yes where you will use the slope of this graph and why?
to find it slope, that can be used further in the formula to calculate the susceptibility
READ ALSO: Magnetic Susceptibility Experiment
13. In which unit system you calculated the value of susceptibility, SI or CGS?
In any unit you can calculate but use similar system for all the variables and constants
14. What is g in the magnetic susceptibility formula and unit of it?
Acceleration due to gravity, SI or CGS as per your calculation
15. What is Gauss Probe and for what purpose we use it?
To measure the magnetic field strength
16. What is an electromagnet, how do we use it to magnetize the material?
Electromagnets are also temporary magnet produced the magnetic field when current flows in the coil. This coil is wrapped on the iron piece of cylindrical shape. When material is placed in between the electromagnets it magnetized this material.
17. Why the FeCl3 liquid in Quincke’s tube rise or fall in the presence of an external magnetic field?
In the case of the FeCl3 liquid in the Quincke’s tube, it contains ions that are both charged and magnetic. When an external magnetic field is applied, these ions experience a force due to their magnetic moment, and this force acts in a direction perpendicular to both the direction of the magnetic field and the direction of the electric current. As a result, the fluid moves either upward or downward depending on the orientation of the magnetic field and the magnetic moment of the ions.
18. Will magnetic field intensity increase after increasing the current of an electromagnet?
Yes, it is directly dependent on it.
19. What signifies the value of the susceptibility in your experiment?
Nature of the FeCl3 material, a ferromagnetic behaviour
20. Can you determine the magnetic susceptibility value of the iron piece from Quincke’s method?
No, because there is no change in the height as per the theory and formula generated from it.
Sources/Information Required to Explain/Understand the Experiment :
1. Atomic Dipole and its Magnetic Moment Concept
2. Magnetization
3. Types of Magnetic Materials
5. Unit system (SI or CGS)
6. Magnetic field and Magnetic Field Intensity Concepts
7. Nature of the Force on the magnetic material (here liquid) in the presence of external magnetic field
Please provide a answer of all the questions
Any Doubt?