不平凡，就不是生活

• Passive components can’t introduce net energy into the circuit. They also can’t rely on a source of power, except for what is available from the (AC) circuit they are connected to. As a consequence they can’t amplify (increase the power of a signal), although they may increase a voltage or current (such as is done by a transformer or resonant circuit). Passive components include two-terminal components such as resistors, capacitors, inductors, and transformers.
• Active components rely on a source of energy (usually from the DC circuit, which we have chosen to ignore) and usually can inject power into a circuit, though this is not part of the definition.^[1]. Active components include amplifying components such as transistors, triode vacuum tubes (valves), and tunnel diodes.

Reference：http://en.wikipedia.org/wiki/Electronic_component

我的理解：

任何必須依靠電流、或電流方向，才能施展其特性的功能者，稱為主動元件，反之則為被動元件。

任何能將功率增幅（Power）的，稱為主動元件，反之為被動元件。

兩者在電路上，皆會通過電子。

【範例】

主動元件：電晶體

被動元件：電阻、電容、電感、變壓器、二極體