Metropolitan Transportation Authority (MTA) Electrical Practice Test

Conductivity is the material’s property that describes how easily electrons can move through it and carry current. It’s a intrinsic characteristic of the substance, with higher conductivity meaning less opposition to current flow. The higher the conductivity, the better the material conducts electricity, which is why metals like copper are used for wires. Conductivity is the reciprocal of resistivity (σ = 1/ρ) and is measured in siemens per meter (S/m). Conductance, by contrast, refers to how easily current flows through a specific path or component and depends on both the material and its size/shape; it’s measured in siemens (S) and is not the material’s intrinsic property. A bus bar is simply a large conductor used to distribute power, and a circuit is a closed loop that current travels through.