Transformers that decrease the voltage are referred to as step-down while those that increase the voltage are referred to as step-up. In reality, transformers do have voltage and current limits, and they are specified in terms of a volt-amp or VA rating which is simply the product of the nominal secondary voltage and maximum allowed secondary current. It simply transforms the power from high-voltage/low-current to low-voltage/high-current (or vice versa), hence the name. This implies that in the ideal case there is no power lost within the transformer. For example, if the secondary-side coil has half as many turns as the primary-side coil then the secondary voltage will be half of the primary voltage and its current will be twice as large as the primary current. Ideally, the voltage is decreased and the current is increased by the ratio of the number of loops between these coils. This flux induces a current in the secondary coil. The current in the primary-side coil creates a magnetic flux in the core. Each side is made up of a coil of wire and these coils are wound around a common magnetic core. In simple terms, a transformer has an input side, or primary, and an output side, or secondary. While a complete exploration of transformers is beyond the scope of this chapter, we can present the basics. The aforementioned voltage scaling issue can be addressed through the use of a transformer. The second item involves smoothing the pulsating DC to produce a constant value, much like a battery. In many cases this means lowering the voltage although there are some applications such as high power amplifiers where the voltage will need to be increased. The first item is the issue of scaling the 120 VAC RMS outlet voltage to a more useful level. On a practical note, there are still two items to consider when it comes to converting AC to DC. \): Transient analysis for halfwave rectifier.
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