大家都知道,电灯的电线,一根叫“火线”,另一根叫“地线”(或“零线”)。在正常情况下,地线上是没有电压的。若用测电笔探测一下,测电笔是不会亮的。但有时也会碰到另一种情况,当测电笔与地线接触的时候,会发出暗光或较强的光来。通常采用的扩大器,输出信号分为两路,其中公用的一条地线,有时也发生类似的情况。这是什么原因呢?简单的说,是地线上有了电压。常用的供电线路,是“三相四线”制,如图中所示,1、2、3三根线叫“火线”,就是普通的三相动力电源线。导线4叫地线。变压器输 Everyone knows that the wires of a light bulb are called “Firewire” and the other is called “ground wire” (or “zero wire”). Under normal conditions, there is no voltage on the ground. If you use a pencil to detect it, the pencil will not light. However, sometimes there is another situation where dark light or strong light is emitted when the pen touches the ground wire. Usually used amplifiers, the output signal is divided into two, in which a common ground, and sometimes a similar situation. What is the reason for this? Simply put, there is a voltage on the ground. The commonly used power supply line is a “three-phase four-wire” system. As shown in the figure, the three lines 1, 2 and 3 are called “FireWire”, which is an ordinary three-phase power line. Wire 4 is called ground wire. Transformer transmission