transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called interdependency induction. If a load is connected to the secondary, an electric current ordain flow in the secondary winding and electrical strenuosity will be transferred from the coil circuit through the transformer to the load. In an ideal transformer, the induced voltage in the alternate winding (VS) is in proportion to the primary voltage (VP), and is given by the proportionality of the number of turns in the secondary (NS) to the number of turns in the primary (NP) as follows: By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) electrical phenomenon to be "stepped up" by making NS greater than NP, klamath river "stepped down" by making NS less than NP. In the vast majority of transformers, the coils are wound around a ferromagnetic core, air-core transformers being a notable exception. Transformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to complexion portions of national creative thinking grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have got eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic inclination designed for household ("mains") voltage. Transformers are essential for high voltage power transmission, which makes long distance transmission economically practical.