Answer the following questions: (a) The earth's magnetic field varies from point to point in space.
Does is also change with time? If so, on what time scale does it change appreciably?
(b) The earth's corei s known to contain iron. Yet geologists do not regard this as a source of earth's magnetism, why?
(c) The charged currents in the outer conducting regions of earth's core are thought to be possible for earth's magnetism. What might be the battery to sustain these currents?
(d) The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologits know about the earth's field in such distant past?
(e) The earth's field departs from its dipole shape substantially at large distances (greater than about 30000km). What agencies may be responsible for this distortion?
(f) Interstellar space has an extremely weak magnetic field of the order of `10^(-12)T`. Can such a weak field be of any significant consequence? Explain.

Explanation

Yes, it changes with the time. On timescale of roughly a few hundred years, the change is appreciable. Even for a smaller scale of just a few years, the variation in Earth.s magnetic field are not completely negligible.