Electrical resistivity and conductivity 1 Ω⋅m. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity, and measures a material's ability to conduct an electric current. It is commonly represented by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) or γ (gamma) are also occasionally used. Its SI unit is siemens per metre (S/m). In an ideal case, cross-section and physical composition of the examined material are uniform across the sample, and the electric field and current density are both parallel and constant everywhere. Many resistors and conductors do in fact have a uniform cross section with a uniform
Electrical contractor classified by three major types of work performed. Electrical contractors employ workers in many capacities, determined by their level of training and experience. Some common jobs include: In the United Kingdom, the two main trade associations are the Electrical Contractors' Association, covering England, Northern Ireland and Wales, and SELECT - the Electrical Contractors' Association for Scotland. The main certification bodies are the National Inspection Council for Electrical Installation Contracting and Elecsa. The National Electrical Contractors Association (NECA) is the largest trade association in the electrical contracting industry, with about 4500 members. NECA publishes an industry magazine, and sponsors an annual