41. What is the
value of the angle of dip at the magnetic equator?
At any place on
magnetic equator, the compass needle remains horizontal &
the value of dip is zero. Hence, the value of dip is minimum
at a place on the magnetic equator.
42. Why should one consider
declination while using a compass needle in most of the earth?
Declination at
a place on the earth's surface is defined as the angle
between the geographical meridian & magnetic meridian at
that place. This value varies from place to place on earth's
surface. In general, its value at a place is constant but
changes very slightly with time. So, one should consider
declination while using a compass needle in most of the
earth.
43. Earth has its terrestrial
magnetism. Does this mean that the core of the earth is a huge
permanent magnet?
Earth has its
terrestrial magnetism. No, this does not mean that the core
of the earth is a huge permanent magnet. Before, earth
is believed to have a huge magnet whose north pole lies to
geographical south pole & south pole lies to geographical
north pole. But at a very high temperature inside the earth,
ferromagnetic material lose their magnetism & becomes
paramagnetic materials so the core of the earth is not a
huge permanent magnet. The latest theory assumes that the
magnetic field of the earth is due to electric current
circulating in its core due to directional current arising
from radioactive heating inside the earth. It is assumed
that the earth behaves as of a magnet is placed inside the
earth.
44.
An iron piece, buried for a long time underground, facing north
south gets magnetized. Why?
As the earth is
believed to have a huge magnet whose north pole lies to
geographical south pole & south pole lies to geographical
north pole. The existence of the earth's magnetic field is
the main cause for an iron piece, buried for a long time
acquire magnetism. The earth's magnetic field is uniform &
if the iron piece is buried, then it is in the uniform
magnetic field. In that field, the magnetic domains of iron
which
are oriented randomly in all directions are forced to
oriented in one direction along the magnetic field of earth.
If an iron piece is buried for long time then magnetic
domains of iron have lost their restoring power and cannot
orient each domain in different direction as at initial
stage. So, magnetic domains of iron are oriented in one
direction. Hence,
an iron piece, buried for a long time underground, facing
north south gets magnetized.
|
