Q. Answer the
following questions regarding earth’s magnetism:
(a) A vector
needs three quantities for its specification. Name the three
independent quantities conventionally used to specify the earth’s
magnetic field.
(b) The angle of
dip at a location in southern India is about 18º.
Would you expect a greater or smaller dip angle in Britain?
(c) If you made
a map of magnetic field lines at Melbourne in Australia, would the
lines seem to go into the ground or come out of the ground?
(d) In which
direction would a compass free to move in the vertical plane point
to, if located right on the geomagnetic north or south pole?
(e) The earth’s
field, it is claimed, roughly approximates the field due to a dipole
of magnetic moment 8 × 1022 J T−1
located at its centre. Check the order of magnitude of this number in
some way.
(f ) Geologists
claim that besides the main magnetic N-S poles, there are several
local poles on the earth’s surface oriented in different
directions. How is such a thing possible at all?
