PHYSICS · Multi-part · CBSE · Physics · Magnetism and Matter · Magnetism and Matter
Problem
Earth’s magnetic field can be modeled, to first approximation, as that of a gigantic bar magnet tilted slightly from the planet’s rotational axis. Imagine, in a purely hypothetical thought experiment, that a planar fault suddenly cleaves Earth along a great circle into two hemispherical shells that immediately drift a short distance apart while retaining their internal structure and domain alignment.
Treat each hemisphere as a rigid body whose magnetic domains were previously continuous across the equatorial plane but are now exposed to space.
(a) Identify the magnetic poles that would appear on the freshly exposed flat faces of the Northern and Southern hemispherical shells. Provide a clear rationale based on the pre-existing dipole orientation of Earth.
(b) Describe qualitatively how the external magnetic field in the vicinity of the equatorial gap would differ from Earth’s original dipole field before the fracture.
(c) Discuss whether the net magnetic dipole moment of the two-hemisphere system, considered as a whole and measured far from the planet, would change in magnitude, direction, or both. Support your answer with physical reasoning.
(d) Real materials resist abrupt reorientation of magnetic domains. Explain qualitatively what energy transformations would accompany the hypothetical cleaving process and why such an event would require or release significant energy.