Magnetic Elements of Earth

Magnetic Elements of Earth:

Magnetic Elements of Earth at a place are the quantities which describe completely in magnitude and in direction, the magnetic field of earth at that place.

Following are three Magnetic Elements of Earth:

  • Magnetic Declination (θ).
  • Magnetic Dip (δ).
  • Horizontal Component (H).

Magnetic Declination:

Magnetic Declination - Magnetic Elements of Earth

The line joining the North and South poles of a freely suspended magnet is called magnetic axis whereas the line joining the geographic North and geographic South direction is called geographic axis.

Magnetic declination (θ) at a place is defined as the angle between the magnetic axis and geographic axis at that place.

A vertical plane passing through the N-S line of the magnet is called a magnetic meridian whereas the vertical plane passing through geographic North and geographic South is called a geographic meridian.

Magnetic declination (θ) at a place is also defined as the angle between magnetic meridian and geographic meridian. The value of magnetic declination at a place is approximately 20°.

magnetic elements diagram - Magnetic Elements of Earth

Magnetic Dip:

It is defined as the angle between total strength of earth’s magnetic field and the horizontal line in magnetic meridian. It is denoted by δ. The value of DIP at a place lies between 0° and 90°. The value of DIP is 90° at poles and 0° at equator.

Horizontal Component:

It is defined as the component of total strength of earth’s magnetic field in the horizontal direction.

In the given figure, ABCD is the magnetic meridian and AB’C’D is the geographic meridian.

∠B’AB = ∠θ is the magnetic declination whereas ∠BAK = ∠δ is the magnetic dip at a place.

Magnetic element Horizontal Component - Magnetic Elements of Earth
Now, Horizontal Component (H) is given by
H = AL = R Cos δ ……….(i)

And, Vertical Component (V) is given by
V = AM = R Sin δ ……….(ii)

Square and add (i) and (ii), we have
H2 + V2 = R2 Cos2 δ + R2 Sin2 δ
⇒ H2 + V2 = R2 (Cos2 δ + Sin2 δ)
⇒ H2 + V2 = R2
⇒ R = √(H2 + V2)

Divide (ii) by (i), we have
V/H = R Sin δ/R Cos δ
⇒ V/H = tan δ

Note: The value of H at a place on the surface of the earth ≅ 3.2 x 10-5 Tesla.

Tangent GalvanometerDerivation of de-Broglie equation
Nuclear ReactorMolecular Orbital Theory
TransformerImperfections or Defects in Solids
Eddy CurrentsAtoms, Molecules and Chemical Arithmetic– NIOS

Leave a Reply

%d bloggers like this: