(a) The earth’s magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

 (b) The earth’s core is known to contain iron. Yet geologists do not regard this as a source of the earth’s magnetism. Why?

(c) The charged currents in the outer conducting regions of the earth’s core are thought to be responsible for earth’s magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Answer –

(a) The Earth’s magnetic field changes throughout time, and it takes a few hundred years for a significant shift to occur.

The change in the Earth’s magnetic field over time cannot be overlooked.

(b) Because the iron core at the Earth’s core is molten and non-ferromagnetic, it cannot be regarded a source of Earth’s magnetism.

(c) Radioactivity in the earth’s interior is the source of energy that keeps the currents flowing in the earth’s core’s outer conducting areas.

The earth’s magnetism is thought to be caused by these charged currents.