UP Board - Class 12 physics - Chapter 5: Magnetism And Matter Handwritten Notes

Magnetism is the phenomenon associated with the force of attraction or repulsion between objects due to their magnetic fields. Matter, when placed in a magnetic field, exhibits varying magnetic properties depending on its atomic structure and alignment of magnetic dipoles.

Key Points:

1. Magnetic Dipole:

   • A magnetic dipole consists of two equal and opposite magnetic poles separated by a distance.
   • Every atom behaves like a magnetic dipole due to the motion of electrons.

2. Magnetic Properties of Materials:

   • Diamagnetic: Materials that are weakly repelled by a magnetic field, e.g., copper, bismuth.
   • Paramagnetic: Materials that are weakly attracted to a magnetic field, e.g., aluminum, platinum.
   • Ferromagnetic: Materials that are strongly attracted to a magnetic field and can retain magnetization, e.g., iron, cobalt, nickel.

3. Magnetization (M):

   • Magnetization is the measure of the magnetic moment per unit volume of a material.
   • It determines the extent to which a material can be magnetized.

4. Magnetic Susceptibility (χ):

   • It is the measure of how a material responds to an external magnetic field.

5. Hysteresis:

   • Ferromagnetic materials exhibit hysteresis, where they retain magnetization even after the external magnetic field is removed.
   • This property is used in creating permanent magnets.

6. Earth’s Magnetism:

   • Earth behaves like a giant magnet with its magnetic field resembling that of a bar magnet.
   • Important elements of Earth’s magnetic field are:
     • Magnetic Declination: Angle between geographic and magnetic meridians.
     • Magnetic Inclination: Angle made by the Earth’s magnetic field with the horizontal.
     • Horizontal Component: The component of Earth’s magnetic field parallel to the surface.

7. Applications of Magnetism in Matter:

   • Magnetic materials are used in electric motors, generators, magnetic storage devices, and transformers.
   • Earth’s magnetic field helps in navigation using compasses.

Conclusion:

The study of magnetism and matter provides a comprehensive understanding of the interaction between magnetic fields and materials. This knowledge is essential for the development of magnetic devices, the understanding of Earth’s magnetic field, and its applications in daily life and industry.

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