For more Subjects
https://www.studymedia.in/fe/notes
,SKNSITS, Lonavala // Engineering Physics [2019-20] // Unit 5 – Magnetism and Superconductivity
Unit 5: Magnetism and Superconductivity
Syllabus
Magnetism
- Origin of magnetism
- Classification of magnetism on the basis of permeability (qualitative)
- Applications of magnetic devices: transformer cores, magnetic storage, magneto-optical
recording
Superconductivity
- Introduction to superconductivity; Properties of superconductors: zero electrical
- resistance, critical magnetic field, persistent current, Meissner effect
- Type I and Type II superconductors
- Low and high temperature superconductors (introduction and qualitative)
- AC/DC Josephson effect; SQUID: basic construction and principle of working; Applications of
SQUID
- Applications of superconductors
Introduction
- Magnetic materials play a prominent role in modern technology. They are widely used in
industry, electronics and storage technologies.
- Magnetic materials can broadly be classified into soft and hard materials. Soft magnetic
materials are easily magnetized and demagnetized and. They are used in AC applications.
Hard magnetic materials retain magnetism on a permanent basis.
- Further, depending on their response to the external magnetic field, magnetic materials can
be broadly classified into three groups: diamagnetic, paramagnetic and ferromagnetic
materials.
5.1.1 Magnetism: basic terms and definitions
1. Magnetic dipole
- Magnetic dipole is generally a tiny magnet of microscopic to subatomic
dimensions generated due to current loop.
- Electrons circulating around atomic nuclei, electrons spinning around their
axes, and rotating positively charged atomic nuclei all are magnetic dipoles.
- Magnetic dipole is referred to smallest magnetic unit having two poles
(north and south) that produces magnetic field and are inseparable from
each other.
- A single monopole has never been observed.
2. Magnetic dipole moment
- The strength of a magnetic dipole is represented by magnetic dipole
moment. It is a measure of a dipole’s ability to align itself according to
direction of external magnetic field.
- The magnetic moment can be considered to be a vector quantity with direction
perpendicular to the current loop in the right-hand-rule direction.
- Magnetic dipole moment is defined as the maximum amount of torque caused by magnetic
force on a dipole that arises per unit value of surrounding magnetic field in vacuum. This
torque is given by
𝜏 = 𝜇 ×𝐵
Page 1 of 21
Other Subjects: https://www.studymedia.in/fe/notes
, SKNSITS, Lonavala // Engineering Physics [2019-20] // Unit 5 – Magnetism and Superconductivity
3. Magnetic field strength (H)
- The strength (or intensity) of magnetic field at any point in magnetic field is force
experienced by a unit north pole placed at that point. It is denoted by H.
- The unit of H is ampere-turns per meter (A/m) in SI system.
4. Magnetization (M)
- Magnetization (or intensity of magnetization) is the measure of magnetism of magnetic
materials. It is defined as magnetic moment per unit volume and denoted by M.
- The unit of magnetization in SI system is amperes per meter (A/m).
- As magnetization is induced by magnetic field, M is proportional to H.
Thus, M H or M = H
Where, is called as magnetic susceptibility.
5. Magnetic Susceptibility ()
- The magnetic susceptibility of a material is a measure of the ease with which the material
can be magnetized. It is defined as magnetization (M) produced in the material per unit
applied magnetic field (H).
- Hence, = M/H
- Materials having high susceptibility are easily magnetized.
6. Magnetic flux ()
- Magnetic flux is a measurement of the total magnetic field which passes through a given
area. The lines of induction are collectively called as flux.
- The SI unit of magnetic flux is the Weber (Wb).
7. Magnetic Induction or magnetic flux density (B)
- A magnetic field is schematically represented by lines of magnetic induction or magnetic flux
density).
- The magnetic flux per unit area is defined as magnetic flux density.
- Magnetic induction is the number of lines of force through a unit area of cross section
perpendicularly.
- Thus, B = /A.
- The SI unit of B is Weber per square meter (Wb/m2) and CGS unit is Tesla (T)
- 1 Gauss = 10-4 Tesla
8. Relation between B and H
When a material is kept in a magnetic field, two types of induction arise – one due to magnetizing
field H and other due to magnetization M of the material itself. The magnetic induction B produced
inside the material is given by
𝐵 = 𝜇0(𝐻 + 𝑀)
Where, 0 is known as permeability of the free space. It is equal to 4x10-7 henry per meter (H/m)
𝐵 = 𝜇 01 + 𝑀 𝐻
𝐻
Or 𝐵 = 𝜇0 1 + 𝐻
Or 𝐵 = 𝜇𝐻
Page 2 of 21
Other Subjects: https://www.studymedia.in/fe/notes
https://www.studymedia.in/fe/notes
,SKNSITS, Lonavala // Engineering Physics [2019-20] // Unit 5 – Magnetism and Superconductivity
Unit 5: Magnetism and Superconductivity
Syllabus
Magnetism
- Origin of magnetism
- Classification of magnetism on the basis of permeability (qualitative)
- Applications of magnetic devices: transformer cores, magnetic storage, magneto-optical
recording
Superconductivity
- Introduction to superconductivity; Properties of superconductors: zero electrical
- resistance, critical magnetic field, persistent current, Meissner effect
- Type I and Type II superconductors
- Low and high temperature superconductors (introduction and qualitative)
- AC/DC Josephson effect; SQUID: basic construction and principle of working; Applications of
SQUID
- Applications of superconductors
Introduction
- Magnetic materials play a prominent role in modern technology. They are widely used in
industry, electronics and storage technologies.
- Magnetic materials can broadly be classified into soft and hard materials. Soft magnetic
materials are easily magnetized and demagnetized and. They are used in AC applications.
Hard magnetic materials retain magnetism on a permanent basis.
- Further, depending on their response to the external magnetic field, magnetic materials can
be broadly classified into three groups: diamagnetic, paramagnetic and ferromagnetic
materials.
5.1.1 Magnetism: basic terms and definitions
1. Magnetic dipole
- Magnetic dipole is generally a tiny magnet of microscopic to subatomic
dimensions generated due to current loop.
- Electrons circulating around atomic nuclei, electrons spinning around their
axes, and rotating positively charged atomic nuclei all are magnetic dipoles.
- Magnetic dipole is referred to smallest magnetic unit having two poles
(north and south) that produces magnetic field and are inseparable from
each other.
- A single monopole has never been observed.
2. Magnetic dipole moment
- The strength of a magnetic dipole is represented by magnetic dipole
moment. It is a measure of a dipole’s ability to align itself according to
direction of external magnetic field.
- The magnetic moment can be considered to be a vector quantity with direction
perpendicular to the current loop in the right-hand-rule direction.
- Magnetic dipole moment is defined as the maximum amount of torque caused by magnetic
force on a dipole that arises per unit value of surrounding magnetic field in vacuum. This
torque is given by
𝜏 = 𝜇 ×𝐵
Page 1 of 21
Other Subjects: https://www.studymedia.in/fe/notes
, SKNSITS, Lonavala // Engineering Physics [2019-20] // Unit 5 – Magnetism and Superconductivity
3. Magnetic field strength (H)
- The strength (or intensity) of magnetic field at any point in magnetic field is force
experienced by a unit north pole placed at that point. It is denoted by H.
- The unit of H is ampere-turns per meter (A/m) in SI system.
4. Magnetization (M)
- Magnetization (or intensity of magnetization) is the measure of magnetism of magnetic
materials. It is defined as magnetic moment per unit volume and denoted by M.
- The unit of magnetization in SI system is amperes per meter (A/m).
- As magnetization is induced by magnetic field, M is proportional to H.
Thus, M H or M = H
Where, is called as magnetic susceptibility.
5. Magnetic Susceptibility ()
- The magnetic susceptibility of a material is a measure of the ease with which the material
can be magnetized. It is defined as magnetization (M) produced in the material per unit
applied magnetic field (H).
- Hence, = M/H
- Materials having high susceptibility are easily magnetized.
6. Magnetic flux ()
- Magnetic flux is a measurement of the total magnetic field which passes through a given
area. The lines of induction are collectively called as flux.
- The SI unit of magnetic flux is the Weber (Wb).
7. Magnetic Induction or magnetic flux density (B)
- A magnetic field is schematically represented by lines of magnetic induction or magnetic flux
density).
- The magnetic flux per unit area is defined as magnetic flux density.
- Magnetic induction is the number of lines of force through a unit area of cross section
perpendicularly.
- Thus, B = /A.
- The SI unit of B is Weber per square meter (Wb/m2) and CGS unit is Tesla (T)
- 1 Gauss = 10-4 Tesla
8. Relation between B and H
When a material is kept in a magnetic field, two types of induction arise – one due to magnetizing
field H and other due to magnetization M of the material itself. The magnetic induction B produced
inside the material is given by
𝐵 = 𝜇0(𝐻 + 𝑀)
Where, 0 is known as permeability of the free space. It is equal to 4x10-7 henry per meter (H/m)
𝐵 = 𝜇 01 + 𝑀 𝐻
𝐻
Or 𝐵 = 𝜇0 1 + 𝐻
Or 𝐵 = 𝜇𝐻
Page 2 of 21
Other Subjects: https://www.studymedia.in/fe/notes
