Earth's Magnetism

Earth's Magnetism

Introduction : We are well aware of the magnetic field lines due to a magnet and the properties of magnetic field. Similarly earth behave like a huge magnet and show the properties similar to that of the bar magnet. In this topic we are going to discuss more about Earth's magnetism. When we hold a magnetic needle freely the needle comes to rest in geographical north and south direction, but if it was free to rotate in horizontal direction then ,it comes to rest making an angle with the horizontal. This indicate that there is an magnetic field on the earth.

Earth's Magnetism

A study of Earth's magnetic field is called as terrestrial magnetism. It is also called as Geomagnetism.

Parameter related to earth's magnetism:

Geographical Axis : A straight line passing through both the pole of the earth is called as Geographical axis.

Geographical meridian : At a give place it is vertical plane passing through the geographic north and south pole of the earth.

Geographic Equator : A plane perpendicular to the geographic axis is called as geographic equator.

Magnetic axis : A straight line passing through both the pole of the earth's magnet is called as Magnetic axis.

Magnetic Meridian :At a give place it is vertical plane passing through the magnetic north and south pole of the earth.

Magnetic Equator : A plane perpendicular to the magnetic axis is called as magnetic equator.

Note : The strength of the earth's magnetic field  on the surface of the earth is of the order of 10-4 tesla.

The direction of magnetic field at any location is specified by following

1) Magnetic Declination : The angle between magnetic meridian and geographic meridian at a place is known magnetic declination.

2) Angle of dip (ф) : The angle between earth's magnetic field at a place and the horizontal is known as the angle of dip at that place.

Magnetic Declination

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