Material Non-Isotropic Conductivity

Non-isotropic conductivity refers to the phenomenon where the electrical conductivity of a material varies with direction. In other words, the material conducts electricity differently in different directions. This property is primarily observed in materials with anisotropic crystal structures or microstructures.

Among the given options, the material that exhibits non-isotropic conductivity is wood.

Explanation

Wood is a natural composite material made up of cellulose fibers embedded in a matrix of lignin. The arrangement of these fibers is not uniform, leading to the anisotropic nature of wood.

In the direction parallel to the grain of wood, the conductivity is relatively low due to the presence of air-filled pores and the insulating nature of the cellulose fibers. However, in the direction perpendicular to the grain, wood exhibits higher conductivity due to the presence of conductive pathways provided by the aligned cellulose fibers.

When an electric current is applied to wood along the grain direction, it encounters obstacles in the form of air-filled pores and non-conductive fibers, resulting in a lower conductivity. On the other hand, when the current is applied perpendicular to the grain, it can travel through the conductive pathways provided by the aligned cellulose fibers, resulting in higher conductivity.

Examples of Isotropic Conductors

- Lead: Lead is a metal that exhibits isotropic conductivity. It conducts electricity equally well in all directions due to its metallic bonding and uniform electron distribution.

- Copper: Copper is another metal that exhibits isotropic conductivity. It is widely used as a conductor due to its high electrical conductivity and uniform electron distribution.

- Brass: Brass is an alloy composed of copper and zinc. Like copper, it also exhibits isotropic conductivity due to the metallic bonding between copper and zinc atoms.

In summary, wood exhibits non-isotropic conductivity due to its anisotropic microstructure, while lead, copper, and brass exhibit isotropic conductivity due to their homogeneous and metallic nature.