Usually low voltages or DC(Direct Current) is used by the electronic circuits, because load does not need very high power and just a few capacitors, resistors, I.C or other components will not require much power to perform their jobs and it will be powered by a 18650 lithium battery or any other battery source with required voltage and current.
A circuit diagram or wiring diagram uses symbols to represent parts of a circuit.
When an open circuit to earth ground is detected, the G.F.I. device immediately opens the voltage source to the device. G.F.I. devices are similar to circuit breakers but are designed to protect humans rather than circuit components.
Circuits use two forms of electrical power: alternating current (AC) and direct current (DC). AC often powers large appliances and motors and is generated by power stations.