Assertion–Reason (Magnetism): Diamagnetic susceptibility is much smaller in magnitude than paramagnetic susceptibility; for both classes the relative permeability μr is close to unity.

Introduction / Context:
Magnetic materials are broadly categorized by their magnetic susceptibility χ and relative permeability μr = 1 + χ. Diamagnets possess small negative χ; paramagnets have small positive χ. Knowing magnitudes and physical origins clarifies many design choices in electromagnetics.

Given Data / Assumptions:

• Diamagnetic χ typically ~ −10^-5 to −10^-6; paramagnetic χ typically ~ +10^-3 to +10^-6.
• μr = 1 + χ for linear, isotropic materials under weak fields.
• No cooperative magnetic ordering (i.e., not ferro/ferri/antiferromagnets).

Concept / Approach:
The assertion states the magnitude of diamagnetic susceptibility is much smaller than that of paramagnetic susceptibility, which is generally true for most elemental and molecular solids. The reason claims μr ≈ 1 for both. While that statement is also true (since |χ| ≪ 1), it does not explain why diamagnetic |χ| is typically smaller than paramagnetic χ. The origins differ: diamagnetism arises from induced currents opposing applied fields (Lenz-like response), whereas paramagnetism arises from alignment of permanent atomic magnetic moments from unpaired spins; the latter mechanism usually yields larger χ.

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