Question:

In a deflection magnetometer, the external magnet should be replaced:

Updated On: Oct 13, 2024
  • always in the direction of resultant of earth
  • always with its axis along E-W
  • along N-S in tan A position
  • always along N-S
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The Correct Option is B

Solution and Explanation

The tangent law on which the principle of working of a deflection magnetometer is based, slates, when two magnetic field F and H act as right angles, then these two fields defects through an angle $ \theta $ which is related. $ F=H\sin \theta $ Earths field is always along the directions of East West direction, therefore the magnet must always be placed with its axis along the direction of East West.
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Concepts Used:

Earth’s Magnetic field

The Earth's magnetic field stretches millions of kilometers into space and resembles a bar magnet. The earth's magnetic pole is positioned between the Northern Pole and the North Pole's Antarctic magnets. That is why a compass magnet's north pole points north (north and south poles attract). 

The Earth's magnetic field extends far and wide, but it is very small in terms of field power. It has a field power of merely 40,000 nT as compared to a refrigerator magnet which has a power of 107 nT.

Theory of Earth’s Magnetism

  • The Dynamo Effect: The outer core of the earth has molten Iron and other heavy elements in liquid form. The inner core solidifies under the influence of gravity. Therefore, the motion of metallic fluids in the outer core of the earth causes an electric current. Thus, the earth gets its own magnetic field lines.
  • Ionization of the Outer Layers: This theory tells us that the rotation of the earth in its own axis produces strong electric current due to the ionization of the outer layers of earth. This produces magnetism due to the movement of the ions. However, the magnetic field will be very weak. The Dynamo Effect is the more acceptable theory.

Components of Earth’s Magnetic Field

These are the components that are responsible for the magnitude and direction of the magnetic field of the earth  at a given location:

  • Magnetic Declination 
  • Horizontal Component of Earth’s Magnetic Field
  • The angle of Dip or Magnetic Inclination