Nootan Solutions Magnetic Field and Earth Magnetism ISC Physics Class-12 Nageen Prakashan

Nootan Solutions Magnetic Field and Earth Magnetism ISC Physics Class-12 Nageen Prakashan Chapter-9 Solved Numericals. Step by step Solutions of Kumar and Mittal ISC Physics Class-12 Nageen Prakashan Numericsls Questions. Visit official Website CISCE for detail information about ISC Board Class-12 Physics

Nootan Solutions Magnetic Field and Earth Magnetism ISC Physics Class-12 Nageen Prakashan Chapter-9, Solved Numericals of Kumar and Mittal

Class: 12
Subject: Physics
Chapter 8: Magnetic Field and Earth Magnetism
Board ISC
Writer /Publications Nootan / Nageen Prakashan/Kumar and Mittal
Topics Solved Numericals of page 441, 442


Theory of Earth’s Magnetism

There is one theory that explains how the earth’s magnetism is caused:

  1. Dynamo effect: The earth gets its own magnetic field lines because of the presence of the metallic fluids that are present at the outer core as well as in the inner core. The outer core consists of molten iron, while the inner core has the solidified elements.

What Causes Earth’s Magnetism?

Earth’s Magnetism is generated by convection currents of molten iron and nickel in the earth’s core. These currents carry streams of charged particles and generate magnetic fields. This magnetic field deflects ionising charged particles coming from the sun (called solar wind) and prevents them from entering our atmosphere. Without this magnetic shield, the solar wind could have slowly destroyed our atmosphere preventing life on earth to exist. Mars does not have a strong atmosphere that can sustain life because it does not have a magnetic field protecting it.

The earth’s magnetic poles are not aligned to the actual geographic north and south poles. Instead, the magnetic south pole is in Canada while the magnetic north pole lies in Antarctica. The magnetic poles are inclined by about 10 degrees to the earth’s rotational axis. So, all this time your compass was really pointing to Canada, not the true North

Components of Earth’s Magnetic Field


There are three components that are responsible for the magnitude as well as the direction of the earth’s magnetic field:

  • Magnetic declination
  • Magnetic inclination or the angle of dip
  • Horizontal component of the earth’s magnetic field

Variations in Earth’s Magnetic Field


  • Secular Variation: The magnetic axis undergoes a periodic change because of its spin around its own axis from east to west. The time cycle of this variation is 960 years.
  • Eleven-year Sunspot Cycle: Once in every eleven years, the earth faces the sunspot which is a region of the strong magnetic field. Thus the magnetic activity of the earth is very much influenced by this variation.
  • Daily and Annual Variation: The ultraviolet rays from the sun ionize the earth’s atmosphere. As a result of which the current is generated which further produces the magnetic field. This is the result of daily and annual variations.
  • Lunar Variations: Apart from the sun, the moon also influences the magnetic activity of earth. Due to the tidal motions of the earth’s ionized layer during a lunar eclipse, there is variation in earth’s magnetic field. This variation is the Lunar Variation.
  • Irregular and Aperiodic Variation: During a particular period of time when the solar activity of the sun is more active, the radiations from the sun ionize the atmosphere of the earth. This causes current when the earth revolves around its own axis resulting in the magnetic field.

Solved Numericals of Magnetic Field and Earth Magnetism Nootan Solutions, Nageen Prakashan Kumar and Mittal



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