Magnetic classification of materials in physics and electrical engineering Evaluate the statement: “Wood is a diamagnetic material.” State whether this is true or false, considering how organic, non-conductive solids interact with external magnetic fields.

Introduction / Context:
This question probes your understanding of magnetic material classification—diamagnetic, paramagnetic, and ferromagnetic—and asks you to place wood, a common organic solid, into the correct category. Correctly identifying diamagnetism is important in materials science and electrical engineering because it influences how materials behave in magnetic fields and in devices like transformers, magnetic sensors, and MRI environments.

Given Data / Assumptions:

• Wood is an organic, largely non-conductive composite of cellulose, hemicellulose, and lignin.
• No intentional magnetic dopants or metallic inclusions are present.
• External fields are moderate (laboratory scale), not strong enough to cause exotic effects.

Concept / Approach:
Diamagnetism is a universal, weak magnetic response arising from induced orbital currents that oppose the applied magnetic field (Lenz’s law at the atomic scale). In diamagnetic materials, magnetic susceptibility chi is negative and very small in magnitude. Paramagnetism (positive, small chi) requires unpaired electron spins. Ferromagnetism (large, positive chi with hysteresis) requires cooperative spin alignment and magnetic domains, which are absent in organic materials like wood.

Step-by-Step Solution:
Identify electronic structure of wood’s constituents: closed-shell molecular orbitals with no persistent unpaired spins → no paramagnetism.Absence of magnetic exchange interactions and crystal structures that support domain formation → no ferromagnetism.Remaining possibility is diamagnetism: tiny, negative susceptibility due to field-induced electron motion opposing the applied field.Therefore, the correct magnetic classification for clean, dry wood is diamagnetic.

Verification / Alternative check:
Handbooks list organic polymers and most biological tissues as diamagnetic. Simple bench demonstrations show negligible attraction to magnets; if any effect is detectable, it is a very slight repulsion in precision balances.

Why Other Options Are Wrong:
“False” contradicts reference data. “True only at cryogenic temperatures” is incorrect; diamagnetism persists at all temperatures. “True only when saturated with water” confuses conductivity with magnetism. “Ferromagnetic” is categorically incorrect for wood.

Common Pitfalls:

• Confusing electrical conductivity with magnetic response.
• Assuming any attraction to a magnet implies ferromagnetism; most materials are weakly dia- or paramagnetic.

Final Answer:
True