EARTH AS A MAGNET

The very fact that a freely suspended magnet points almost north and south that there is some force which directs the suspended magnet to point that way.

This can be easily explained if earth is considered as a huge magnet, with its south-pole somewhere near the North geographical pole and north pole near the south geographical pole.

Earth as a huge magnet

Still, the location of South, magnetic pole may be about 1600 km from the north geographical pole. The exact location of the earth's magnetic north pole has not been discovered.

Because the earth's magnetic South and geographical North pole do not coincide and also due to the presence of magnetic materials in the earth, the north-pole of a compass needle points to the true geographical north at only a few places on the surface of the earth.

The variation between the direction in which the north-pole of the compass needle points and the true north is known as the Declination. This Angle of Declination varies at different places on the surface of earth; also, the amount of this variation changes slightly from time to time.

Magnetic Declination and
Angle of Declination

When a compass needle is freely suspended, its plane does not lie parallel to the earth's surface but makes an angle with the horizontal. This angle is known as the DIP of the magnetic needle.

The Angle of Dip also varies with different places on the surface of earth and also varies slightly with time.

Angle of Dip

Naturally, Dip is minimum at places near the equator and goes on increasing with latitude.