Final answer:
The line connection terminals on a 120-volt receptacle are part of a three-wire system including a live/hot wire, a neutral wire, and an earth/ground wire. These terminals ensure the proper and safe function of electrical appliances and the correct color-coding of wires, which varies by region, identifies each wire type.
Step-by-step explanation:
The line connection terminals on a 120-volt receptacle are critical for ensuring the safe and proper function of the three-wire system used in standard electrical installations. A standard three-hole outlet includes a three-prong plug that can only be inserted one way, which facilitates the correct continuity and safety of the electrical device or appliance connected to it. The wiring system includes a live/hot wire, a neutral wire, and an earth/ground wire.
The color-coding of the insulating plastic on these wires is used to identify each one; however, these color codes can vary around the world. Typically, the live/hot wire may be brown, red, black, blue, or grey, while the neutral wire might be blue, black, or white. The earth/ground wire is often green but can be yellow or a bare wire. It is essential to determine the specific color code in your region for correct identification and connection of wires.
In the context of the three-wire system, the neutral wire is connected to earth/ground at the voltage source and the user's location, making it at zero volts relative to the earth, ensuring that it is safe to touch even when the insulation is compromised. The live/hot wire supplies the essential voltage and current for the appliance's operation. Moreover, there's a third connection to earth/ground which is made to the case of the appliance to ensure it is also at zero volts.