The transformer is such an apparatus for energy conversion.
The transformer is used to convert alternating voltage from a value on an input to a different value at an output. It can only transform alternating current and the frequency is identical at the entrance and exit. Characteristic of all energy conversion is that the effect is theoretically unaffected by the transformation. In practice, however, all energy conversion entails heat loss. For the transformer this means that the voltage times the current at the output is equal to voltage times current at the input, subtracted heat loss.Electrical energy conversion where there is a need to convert the frequency, is now using modern power electronics. The central component of a power electronic converter is the power semiconductor.
