Elements of Earth's Magnetic Field
Category : JEE Main & Advanced
The magnitude and direction of the magnetic field of the earth at a place are completely given by certain. quantities known as magnetic elements.
(1) Magnetic Declination \[(\theta )\]: It is the angle between geographic and the magnetic meridian planes.
Declination at a place is expressed at \[{{\theta }^{o}}E\] or \[{{\theta }^{o}}W\] depending upon whether the north pole of the compass needle lies to the east or to the west of the geographical axis.
(2) Angle of inclination or Dip \[(\phi )\] : It is the angle between the direction of intensity of total magnetic field of earth and a horizontal line in the magnetic meridian.
(3) Horizontal component of earth's magnetic field \[({{B}_{H}})\] : Earth's magnetic field is horizontal only at the magnetic equator. At any other place, the total intensity can be resolved into horizontal component \[({{B}_{H}})\] and vertical component \[({{B}_{V}})\].
Also \[{{B}_{H}}=B\cos \phi \] ...... (i) and \[{{B}_{V}}=B\sin \varphi \] ...... (ii)
By squaring and adding equation (i) and (ii) \[B=\sqrt{{{B}_{{{H}^{2}}}}+{{B}_{{{V}^{2}}}}}\]
Dividing equation (ii) by equation (i) \[\tan \varphi =\frac{{{B}_{V}}}{{{B}_{H}}}\]
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