Magnetism & Matter Class 12 Physics Chapter 5 One Shot | New NCERT CBSE

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The lesson on Magnetism and Matter for Class 12 Physics is condensed into a single video on the Lno Haab Free Learning Platform, exploring the origin of magnets from the island of Magnesia in Greece and various properties of magnets, including magnetic attraction and field lines. The text covers different types of magnets and materials based on their magnetic properties, explaining how ferromagnetic, paramagnetic, and diamagnetic substances interact with external magnetic fields and provide examples of each.

Insights

The term "magnet" originated from the island of Magnesia in Greece due to its magnetic nature, with a shepherd facing magnetic difficulty in 600 BC.
Magnets have distinct properties, including always aligning in the North-South direction, showcasing magnetic attraction and repulsion between poles.
Materials are classified as diamagnetic, paramagnetic, or ferromagnetic based on their magnetic properties, with examples like iron nails and copper illustrating these distinctions.

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Recent questions

What is magnetism?
Magnetism is a natural phenomenon where materials exert attractive or repulsive forces on other materials.

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Summary

00:00

Magnetism: Ancient Origins and Modern Applications

Magnetism and Matter lesson for Class 12 Physics is condensed into one video on the Lno Haab Free Learning Platform.
The term "magnet" originated from the island of Magnesia in Greece due to its magnetic nature.
The story dates back to 600 BC, where a shepherd in Magnesia faced difficulty moving due to magnetic shoes and sticks.
The concept of magnetic attraction from deposits under the island was discovered.
Magnetism is prevalent in various devices like fridge magnets, bar magnets, and metro train doors.
In ancient China, Emperor Huang Tie used a magnet in his chariot to always point south, aiding in winning battles.
Magnets have distinct properties, including always aligning in the North-South direction when freely suspended.
Isolated poles in a magnet do not exist; North and South poles always come in pairs.
Like poles repel, while unlike poles attract, showcasing the magnetic properties of magnets.
Magnetic field lines form closed continuous loops around a bar magnet, with no intersections, indicating the strength and direction of the magnetic field.

16:18

Magnetic Fields and Bar Magnets Explained

Magnetic field in the middle space is empty, with weak field lines causing repulsion between North poles.
Magnetic field lines never intersect, creating unique tangents at points of intersection.
A circular current-carrying loop acts as a magnetic dipole, with Sita and Geeta observing opposite directions of current flow.
Magnetic moment of the loop is given by i * a, where i is current and a is area.
A bar magnet is a collection of circulating loops similar to solenoids, with the same magnetic field and moment.
Magnetic field at a far axial point of a solenoid is given by /4π * 2m/r, where m = n * i * a.
Experimentally, the magnetic field and moment of a bar magnet are equivalent to a solenoid.
Bar magnets have North and South poles, with magnetic field lines forming continuous loops.
Torque on a compass needle in a magnetic field is given by m * B * sinθ, causing deflection.
Equilibrium of the needle involves balancing deflection torque with restoring torque, given by I * α.

33:46

Understanding Simple Harmonic Motion in Magnetism

The equation d theta / dt2 is used instead of omega, with opposite torques acting in opposite directions.
Deflection does not necessarily mean a high value of theta, as it may not reach a complete 180 degrees.
For very small values of theta, theta can be approximated as theta.
The equation of motion resembles simple harmonic motion (SHM), with d2s theta / dt2 = - m b theta.
Comparing the equations reveals that the motion is simple harmonic.
The value of omega can be found as omega = mb1 / a.
Omega can be written as the angular frequency, 2p / t, in simple harmonic motion.
The magnetic potential energy is the energy possessed by a magnetic compass in a magnetic field.
The value of magnetic potential energy changes as theta changes, with specific cases where it is zero, minimum, or maximum.
The analogy between electrostatics and magnetism includes similarities in terms of magnetic moment, equatorial and axial fields, torque, and magnetic potential energy.

53:02

Understanding Magnetic Properties in Materials

The needle inside a magnetic compass pivots on the center, moving on a horizontal plane.
Solenoids are associated with magnetic moments and are denoted by a capital N for the total number of turns.
The magnetic moment is calculated based on the number of turns, amperes, and area given.
The force and torque on solenoids in a horizontal magnetic field are determined by the angle of the field.
Magnetization refers to the total magnetic moment within an object's unit volume.
Magnetic intensity, denoted by H, is the magnetizing force and is proportional to magnetization.
Magnetic susceptibility indicates how a material responds to an applied magnetic field, either attracting or repelling.
Susceptibility is mathematically represented as the ratio of magnetization to magnetic intensity.
Permeability signifies a material's ability to establish a magnetic field within itself.
Materials are classified as diamagnetic, paramagnetic, or ferromagnetic based on their magnetic properties.

01:11:23

Magnetic Properties of Different Substances

Diamagnetic substances have a negative value of magnetic susceptibility, repelling from applied magnetic fields.
Paramagnetic substances have a positive value, being attracted to magnetic fields but with a smaller effect.
Ferromagnetic substances have a positive value as well, strongly magnetizing in the presence of an applied field.
Diamagnetic substances move from stronger to weaker magnetic field regions, avoiding strong fields.
Paramagnetic substances align their constituent particles in the direction of an applied field, attracting but not as strongly as ferromagnetic substances.
Ferromagnetic substances form domains where particles align, leading to strong attraction in the presence of an external field.
Hard ferromagnets retain magnetization even after the external field is removed, like Alnico used in permanent magnets.
Soft ferromagnets lose magnetization once the external field is removed, such as soft iron used in electromagnets.
Examples of diamagnetic materials include copper, gold, and water, which do not attract magnets.
Examples of ferromagnetic materials include iron nails, which strongly attract magnets, distinguishing them from non-magnetic materials like paper or copper.

01:27:58

"Magnetic Properties of Materials and Calculations"

Ferromagnetic materials are strongly attracted by magnets, while paramagnetic materials are weakly attracted. Diamagnetic materials are not attracted by magnets, leading to the classification of materials based on their magnetic properties.
Examples of paramagnetic materials include aluminum, platinum, chromium, manganese, copper, and sulphate. Ferromagnetic materials consist of iron, nickel, cobalt, or alloys of these metals, commonly seen in items like iron nails and magnets.
In a problem involving a toroid solenoid with 3000 turns and a mean radius of 10 cm, and a soft iron core with a relative permeability of 2000, the magnetic field strength (B) is calculated to be 12 Tesla.
Another problem presents a magnetizing field of 1600 amperes producing a magnetic flux of 2.4 * 10^-5 Weber. By calculating the magnetic susceptibility parameter (kai), the value is determined to be 7.5 * 10^-4 Tesla per ampere meter.

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