variac-a piece of test equipment that provides a variable output voltage.the variac is plugged into the 20-V power line and the equipment under test is plugged into the Variac.most Variacs avaible today have an isolated output.
volt-ampere(VA)-the unit of apparent power that specifies the power rating of a transformer.the product VA is called the apparent power because it is the power that is apparently used by thw transformer.