【简答题】It is abstraction that allows us to ignore the internal details of a complex device such as a computer, automobile, or microwave oven and use it as a single, comprehensible unit.
【简答题】An electric circuit often consists of four parts: a source such as a _______(电池) , the conductors , the control device such as a _______ (开关) , and a _______ (负载) .