Question

Discuss Earth’s magnetic field in detail.

Answer 1

1. William Gilbert proposed that Earth behaves like a gigantic powerful bar magnet.
2. The temperature inside the earth is very high, so it is not possible for a magnet to retain its magnetism.
3. Gover suggested that the Earth’s magnetic field is due to hot rays coming out from the sun.
4. The branch of physics which deals with the Earth’s magnetic field is called Geomagnetism or Terrestrial magnetism.
5. Three quantities required to specify the Earth’s magnetic field are
   • magnetic declination (D)
   • magnetic dip or inclination (I)
   • the horizontal component of the Earth’s magnetic field (B_H)
6. B_E → Earth’smagneticfield.
   B_H → Horizontal component
   B_V → Vertical component
   Horizontal component B_H = B_E cos I
   Vertical component B_V= B_E sin I;
   tan I = `"B"_"v"/"B"_"H"`
   i) At magnetic equator B_H = B_E [I = 0°]
   B_V = 0
   ii) At magnetic poles B_H = 0 [I = 90°]
   B_V = B_E