THE BASICS OF MAGNETISM the detailed explanation of magnetism and its related properties for a good seminar purpose

here is the detailed explanation of magnetism and its related properties for a good seminar purpose

1. THE BASICS OF MAGNETISM Comprehensive Overview of Magnetic Principles Presented by Kumaresh P Research Scholar SRM IST, VDP Campus, Chennai - 26 Date: 19.09.2025 19-09-2025 1

2. 19-09-2025 2 Historically the word ‘magnetism’ was derived from iron ore magnetite (Fe 3 O 4 ). In olden days, magnets were used as magnetic compass for navigation, magnetic therapy for treatment and also used in magic shows. In modern days, we use them in Motors, cycle dynamo, loudspeakers, magnetic tapes used in audio and video recording, mobile phones, head phones, CD, pen-drive, hard disc of laptop, refrigerator door, generator etc. MAGNETISM FROM THE MAGIC TO MODERN DAY

3. 19-09-2025 3 Earlier, both electricity and magnetism were thought to be two independent branches in physics. In 1820, H.C. Oersted observed the deflection of magnetic compass needle kept near a current carrying wire. This unified the two different branches, electricity and magnetism as a single subject ‘electromagnetism’ in physics. ACCIDENT TO ADVANCEMENT

4. 19-09-2025 4 MAGNETIC DIPOLE MOMENT (M d ) A system having two opposite magnetic poles separated by a distance   is called as a magnetic dipole. The magnetic dipole moment is defined as the product of its pole strength and magnetic length. where,  - magnetic pole strength  - length of the magnet A lso,   - electric current - area of cross section . 2. MAGNETIC FIELD (B) The magnetic field at a point is defined as a force experienced by the bar magnet of unit pole strength  

5. 19-09-2025 5 3. MAGNETIC FIELD LINES The imaginary representation of the magnetic field in a space are called magnetic field lines. 4. MAGNETIC FLUX ( Φ B ) The number of magnetic field lines crossing any area normally is defined as magnetic flux Φ B through the area.

6. 19-09-2025 6 Magnetising field: The magnetic field which is used to magnetize a sample or specimen is called the magnetising field. Magnetising field is a vector quantity and is denoted by and its unit is Am –1 . Magnetic permeability: The magnetic permeability is the measure of ability of the material to allow the passage of magnetic field lines through it or the degree of penetration of magnetic field through the substance - absolute permeability - permeability of the medium - relative permeability    

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8. 19-09-2025 8 For free space, the relative permeability is any bulk material contains a large number of atoms. Each atom consists of electrons which undergo orbital motion . Due to orbital motion, electron has magnetic moment and these magnetic moments orient randomly. Therefore, the net magnetic moment per unit volume of the material is zero . When such a material is kept in an external magnetic field, atomic dipoles are induced and they will try to align partially or fully along the direction of external field. The net magnetic moment per unit volume of the material is known as intensity of magnetization.    

9. 19-09-2025 9 Magnetic susceptibility: The ratio of the intensity of magnetization induced in the material to the magnetizing field  

10. 19-09-2025 10 RIGHT- HAND RULE

11. 19-09-2025 11 Magnetic Domains What are Magnetic Domains? Regions within magnetic materials where atomic magnetic moments are aligned in the same direction Domain Behavior: Unmagnetized state:  Domains point in random directions External field applied:  Domains align with field direction Domain walls:  Boundaries between differently oriented domains Saturation:  All domains aligned with external field Magnetic domains: Random alignment (left) vs. aligned under external field B₀ (right)

12. 19-09-2025 12 Hysteresis Loop & Magnetic Properties Key Properties: Coercivity ( Hc ):  Magnetic field needed to reduce magnetization to zero Retentivity (Br):  Magnetization remaining when external field is removed Saturation (Bs):  Maximum magnetization achieved Hard Materials:  High coercivity, retain magnetization Soft Materials:  Low coercivity, easy to magnetize/demagnetize

13. 19-09-2025 13 Applications of Magnetism Electric Motors - Use electromagnetic induction to convert electrical energy to mechanical energy Generators - Convert mechanical energy to electrical energy using changing magnetic fields Transformers - Use magnetic cores to transfer energy between electrical circuits MRI Machines - Use strong magnetic fields (1.5-3 Tesla) to align protons for medical imaging Navigation - Compasses use Earth's magnetic field for navigation and direction finding Data Storage - Hard drives and magnetic tapes use magnetic materials for information storage

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15. 19-09-2025 15 Summary & Conclusions Key Takeaways Magnetism  is a fundamental force involving magnetic fields and materials Five types  of magnetic behavior: diamagnetic, paramagnetic, ferromagnetic, antiferromagnetic, ferrimagnetic Magnetic domains  explain how materials become magnetized Hysteresis loops  show magnetic memory and energy loss Applications  span from everyday items to advanced technology Modern materials  enable high-tech applications in energy and medicine