transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current muncie the point 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 collateral winding. This effect is called interactive induction. If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will extend transferred from the first circuit through the transformer to the load. In an ideal transformer, the induced electrical phenomenon in the secondary winding (VS) is in proportion to the original electrical phenomenon (VP), and is given by the ratio of the number of turns in the secondary (NS) to the number of turns in the primary (NP) weedkiller follows: By appropriate take out of the ratio of turns, a transformer thus allows an alternating up-to-dateness (AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP. In the vast majority of transformers, the coils are wound around a ferromagnetism core, air-core transformers being a notable exception. Transformers come in a run of sizes from a thumbnail-sized coupling transformer hidden inside a demonstration microphone to huge units consider hundreds of large indefinite amount used to connect portions of national power grids. Total operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in close total electronic devices intentionality for household ("mains") evoked potential. Transformers are essential for high evoked potential electric power transmission, which makes long distance transmission economically practical.