Physics
Electrical Conductivity
Quick fact
Silver is the best natural conductor, but copper is used in most wiring because it is cheaper and almost as conductive. Surprisingly, diamond, which is an insulator, can become a conductor when doped with certain impurities.
Why this is interesting
You know that a copper wire can light a bulb, but a rubber band cannot—why do some materials let electricity flow while others block it?
Read the full explanation
Understanding Electrical Conductivity
Imagine water flowing through pipes: the water represents electric current, and the pipe represents the material. Electrical conductivity is how easily water (current) can flow. In a material, atoms are arranged in a lattice, and some atoms have loosely held outer electrons that can break free and move around. In metals, these 'free electrons' form a sea of charge carriers that drift when you apply a voltage. The more free electrons available and the less they are scattered by atoms, the higher the conductivity. This is why metals like copper and aluminum are good conductors, while materials like rubber, which tightly hold their electrons, are insulators.
A deeper explanation
At the atomic level, electrical conductivity arises from the availability and mobility of charge carriers. In metals, atoms contribute one or more valence electrons to a shared 'sea' that can move freely. When an electric field is applied, these electrons drift in the opposite direction to the field, creating a net current. The conductivity (σ) is inversely related to resistivity (ρ) and depends on the number of free electrons per unit volume (n), their charge (e), and their mobility (μ): σ = n e μ. Mobility is reduced by collisions with vibrating atoms (phonons) and impurities, which is why increasing temperature generally decreases conductivity. Understanding this mechanism is key to designing materials for specific applications—from highly conductive wires for power grids to insulating coatings for safety, and to the development of semiconductors that power modern electronics.