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| Figure 1-18 Transformer nameplate. |

| there may be other types of identifications for various gauges, temperature indication, pressure, drains, and various valves. |

| Thus, it can be seen that while the transformer consists primarily of a primary and a secondary winding, there are many other factors to take into consideration when selecting a transformer for a particular use. Most power supply transformers are designed to operate at a frequency of 50 or 60 cycles per second. Aircraft and other special application transformers are designed for a frequency range from 400 to 4000 cycles per second. The higher frequencies permit a saving in size and weight of transformers and associated equipment; further, where separate circuits prove economical, fluorescent lighting at the higher frequencies has been found to be more efficient. |

| Review |

| 1. The transformer is a device, having no moving parts, which transfers electric power from one circuit to another by electromagnetic means, usually with changes in values of both current and voltage. They may be used to step up or step down input voltage. Its operation depends on the relationship between magnetism and electricity. |

| 2. An electric current flowing in a conductor produces a magnetic field around that conductor (Fig. 1-3). The magnetic field can be concentrated and increased in strength if the conductor is made into a loop (Fig. 1-4), and further increased if several loops are made into a coil (Fig. 1-5). The magnetic field can be increased appreciably if an iron or steel core is inserted inside the coil (Fig. 1-6). |

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