In the context of resistivity, it is crucial to understand the intrinsic factors that affect it. Resistivity is a material property that indicates how strongly a material opposes the flow of electric current. It is primarily influenced by:

• Atomic structure: The arrangement and type of atoms in a material inherently affect its resistivity. Materials with tightly bound electrons in full outer shells, for example, resist electron flow more than those with free electrons in their atomic structure.
• Material type: Different materials have different inherent electrical properties. Conductors (like copper) have low resistivity, while insulators (like rubber) have high resistivity due to differing atomic structures and electron mobility.
• Temperature: Temperature variations can affect how easily electrons can move through a material. Generally, the resistivity of a conductor increases with temperature.

However, the length of the conductor is not a factor that affects the resistivity itself. Instead, resistivity is a property independent of the physical dimensions of the material. The length of the conductor affects resistance, not resistivity. Resistance is calculated using the formula:

R = ρ × (L/A)

where R is resistance, ρ is resistivity, L is the length of the conductor, and A is the cross-sectional area. Thus, while length is integral to calculating resistance, it does not alter the inherent resistivity of the material.

Therefore, the correct answer to the question of which factor does NOT affect resistivity is the Length of the conductor.