Notes from Toppers

Diamagnetic, Paramagnetic And Ferromagnetic Materials:

  • Magnetic materials classification: Diamagnetic materials: Substances that are weakly repelled by magnetic fields. Examples include copper, silver, and gold. Paramagnetic materials: Substances that are weakly attracted to magnetic fields. Examples include aluminum, magnesium, and oxygen. Ferromagnetic materials: Substances that are strongly attracted to magnetic fields and can retain their magnetism even after the magnetic field is removed. Examples include iron, nickel, and cobalt.

  • Diamagnetism - explanation and examples:

  • Diamagnetism occurs due to the cancellation of magnetic moments of paired electrons. All paired electrons in a diamagnetic material have their spins paired in opposite directions, resulting in a net magnetic moment of zero.
  • They weakly oppose an external magnetic field.
  • Paramagnetism - explanation and examples:
  • Paramagnetism occurs due to the presence of unpaired electrons in a material. Unpaired electrons have a net magnetic moment, and when these moments are aligned, they result in a net magnetic field.
  • The paramagnetic behavior is temperature dependent and inversely proportional, as temperature increases, the degree of paramagnetism decreases.
  • Ferromagnetism - explanation, Curie temperature, and examples:
  • Ferromagnetism is the most substantial form of magnetism. It occurs in materials where the unpaired electrons neighboring atoms align in the same direction, creating strong magnetic domains.
  • They can retain their magnetism even after the magnetic field is eliminated because the magnetic domains remain aligned.
  • Curie temperature: The temperature at which a ferromagnetic material loses its ferromagnetism and becomes paramagnetic.

Magnetic Field Of The Earth:

  • Geomagnetic field overview and its importance:
  • The space around Earth where its magnetic influence can be detected is known as the geomagnetic field.
  • It is vital for life on Earth, protecting the planet from harmful solar radiation and enabling animal navigations.
  • Earth’s magnetic poles and shifting:
  • Earth’s magnetic field closely resembles a dipole (a magnet with two poles) with a north-seeking pole and a south-seeking pole.
  • These poles are not fixed and can shift over time. The magnetic north pole has been drifting steadily toward Siberia.
  • Magnetic declination and inclination:

    • Magnetic declination: The angle between true north and the direction indicated by a compass needle. It varies depending on the location.
    • Magnetic inclination or dip angle: The angle between the Earth’s magnetic field lines and the horizontal plane.
  • Magnetic storms and their effects:

  • Intense geomagnetic storms can disrupt power grids, communication systems, and damage satellites.
  • They occur due to solar flares and coronal mass ejections from the sun.
  • Earth’s magnetic field generation - Dynamo theory:
  • The dynamo theory explains the generation and maintenance of Earth’s magnetic field.
  • It suggests that the Earth’s rotation and convection currents within the conductive liquid outer core create a self-sustaining dynamo effect, generating the magnetic field.
  • Applications of Earth’s magnetic field (compasses, navigation, etc.):
  • Used in compasses, navigation, measuring magnetic properties, and as a geologic survey.
  • Palemagnetism provides insights into Earth’s history, tectonic movements, and reconstructions.
  • The magnetic field also guides migratory animals’ movements.

References:

  • NCERT class 11 Physics, Chapter 6: Magnetic Effects of Current and Magnetism.
  • NCERT class 12 Physics, Chapter 5: Magnetism and Matter.