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transformer

transformer, electrical device used to transfer an alternating current or voltage from one electric circuit to another by means of electromagnetic induction. The simplest type of transformer consists of two coils of wire, electrically insulated from one another and arranged so that a change in the current in one coil (the primary) will produce a change in voltage in the other (the secondary). In many transformers the coils are wound on a core made of a material with high magnetic permeability; this intensifies the magnetic field induced by the current in the primary, increasing the transformer's efficiency. Neglecting power losses (which are made small by careful design), the ratio of primary voltage to secondary voltage is the same as the ratio of the number of turns in the primary coil to the number of turns in the secondary coil. The primary and secondary currents are in inverse proportion to the number of turns in the coils. The primary and secondary impedances are in the same ratio as the squares of the numbers of turns in the primary and secondary coils. For example, if a 10-volt, 2-ampere alternating current were to flow through a 10-turn primary of a transformer, theoretically a 20-turn secondary would exhibit a 20-volt, 1-ampere alternating current, with the output impedance four times as great as the input impedance. Transformers are frequently classified according to their uses; the details of construction depend on the intended application. Power transformers are generally used to transmit power at a constant frequency. Audio transformers are designed to operate over a wide range of frequencies with a nearly flat response, i.e., a nearly constant ratio of input to output voltage. Radio frequency (RF) transformers are designed to operate efficiently within a narrow range of high frequencies.

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Transformer

Transformer

A transformer is an electrical device used to change the voltage in an electric circuit. It usually consists of a soft iron core with a rectangular shape. An incoming wire (the primary coil) is wrapped around one side of the core, and an outgoing wire (the secondary coil) is wrapped around the opposite side of the core. Each wire is wrapped around the core a different number of times.

A transformer works on the principle of inductance. An alternating electric current entering the transformer through the primary coil creates a magnetic field within the iron core. The strength of the magnetic field depends on the strength of the electric current.

Once the magnetic field is established in the iron core, the reverse effect occurs in the secondary coil at the opposite side of the core. The oscillating (vibrating) magnetic field within the core creates an electric current in the secondary coil. The strength of the electric current is determined by the number of times the outgoing wire is wrapped around the iron core.

A transformer can be used either to increase or decrease the voltage in a circuit. A transformer of the former type is known as a step-up transformer; one of the latter type is known as a step-down transformer.

Applications

Transformers are used widely in everyday situations. The transmission of electric current from its source (such as a hydroelectric dam) to the consumer can be accomplished most efficiently at high voltages. The high-tension wires one sees overhead in the open country carry electric current at high voltage. But most household appliances operate at much lower voltages. It is necessary, therefore, to install transformers near the point where electric current enters a house or within appliances themselves.

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transformer

transformer Device for converting alternating current at one voltage to another voltage at the same frequency. It consists of two coils of wire coupled together magnetically. The input current is fed to one coil (the primary), the output being taken from the other coil (the secondary).

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transformer

trans·form·er / transˈfôrmər/ • n. 1. an apparatus for reducing or increasing the voltage of an alternating current. 2. a person or thing that transforms something.

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transformer

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