Magnetism and matter revision in 20 minute || Class 12 Chapter 5 Physics Abhishek sahu sir

Summary

This video explains the properties of different magnetic materials: diamagnetic, paramagnetic, and ferromagnetic substances. It covers their behavior in magnetic fields, how temperature affects their magnetic properties, and how they react to varying magnetic field strengths. Diamagnetic materials are repelled by fields, paramagnetic materials are weakly attracted, and ferromagnetic materials are strongly attracted. The video also emphasizes the importance of understanding these concepts for board exams, especially focusing on the NCERT curriculum and excluding Earth's magnetism from the syllabus.

Takeaways

• 😀 Diamagnetic materials have a relative permeability slightly less than 1, indicating their weak repulsion to magnetic fields.
• 😀 Paramagnetic materials have a relative permeability slightly greater than 1, showing a weak attraction to magnetic fields.
• 😀 Ferromagnetic materials have a much greater relative permeability, indicating strong attraction to magnetic fields.
• 😀 The magnetic susceptibility of diamagnetic materials is negative, while for paramagnetic and ferromagnetic materials, it is positive.
• 😀 Temperature changes do not affect the magnetism of diamagnetic substances due to electron pairing that cancels out magnetic moments.
• 😀 For paramagnetic materials, an increase in temperature leads to a decrease in magnetization, showing an inverse relationship.
• 😀 Ferromagnetic materials retain their magnetization at lower temperatures, but above a certain temperature (Curie temperature), magnetization decreases.
• 😀 Diamagnetic substances are repelled by magnetic fields and tend to move toward regions with weaker magnetic fields.
• 😀 Paramagnetic substances are weakly attracted to magnetic fields and move toward stronger magnetic field regions.
• 😀 Ferromagnetic substances are strongly attracted to magnetic fields and prefer moving towards regions of stronger fields.
• 😀 In magnetic field lines, diamagnetic substances cause the lines to bend outward, paramagnetic substances allow them to pass through with reduced intensity, and ferromagnetic substances cause the lines to become densely packed within them.

Q & A

What is the primary difference between diamagnetic, paramagnetic, and ferromagnetic substances?

Diamagnetic substances show weak repulsion to magnetic fields, with relative permeability less than 1. Paramagnetic substances are weakly attracted to magnetic fields, with relative permeability slightly greater than 1. Ferromagnetic substances are strongly attracted to magnetic fields, with relative permeability much greater than 1.

How does temperature affect the magnetism of diamagnetic substances?

For diamagnetic substances, temperature has no significant effect on their magnetism because the magnetic moments of electrons cancel each other out.

What happens to the magnetism of paramagnetic substances as temperature increases?

As temperature increases, the magnetism of paramagnetic substances decreases. This is because the alignment of magnetic moments weakens at higher temperatures.

What is the effect of temperature on the magnetism of ferromagnetic substances?

In ferromagnetic substances, increasing temperature initially has little effect, but after reaching a certain temperature (known as the Curie temperature), the magnetism decreases as temperature continues to rise.

What is the Curie temperature?

The Curie temperature is the critical temperature at which ferromagnetic substances lose their strong magnetic properties and transition to a paramagnetic state.

How do diamagnetic substances respond to magnetic fields?

Diamagnetic substances are repelled by magnetic fields, with the magnetic field lines being bent away from them.

How do paramagnetic substances interact with magnetic fields?

Paramagnetic substances are weakly attracted to magnetic fields, and the magnetic field lines pass through them, although with less intensity than in ferromagnetic substances.

How do ferromagnetic substances behave in the presence of a magnetic field?

Ferromagnetic substances are strongly attracted to magnetic fields, causing the magnetic field lines to become crowded inside the material.

How do the magnetic properties of materials change with their state (solid vs liquid)?

In a magnetic field, diamagnetic liquids will try to move away from strong fields, while paramagnetic and ferromagnetic liquids will move towards stronger fields, with ferromagnetic substances exhibiting the strongest attraction.

What are the key insights to remember about magnetic substances for NCERT-based exams?

For NCERT-based exams, it is important to focus on the properties of diamagnetic, paramagnetic, and ferromagnetic substances. Earth’s magnetism has been removed from the syllabus, so it is sufficient to study the material provided in the curriculum for these topics.