There is voltagetoground between ground part of electric equipment and point of zero electric potential of earth.
电气设备的接地部分与大地零电位点之间存在对地电压。
2
Because you need both a voltage source and a ground in order to create a complete circuit, you need to have a sourcing input or output connected to a sinking output or input.
因为在一个完整的电路中必须有一对电源和地。
3
With this shield in place, the noise current generated by the electrostatic voltage source and the coupling capacitance flows through the shield toground rather than through the signal conductors.