The purpose of the neutral wire in a 4-wire system is

• A. An alternative to a grounded system
• B. To provide a return path to the source
• C. To work in conjunction with the safety ground
• D. None of the above.

Answer: (B)

In a four-wire system, the neutral wire provides a return path for current back to the source, completing the circuit for loads connected from a hot conductor to neutral. This allows normal operation of devices that rely on line-to-neutral voltages (for example, 120 V loads in a system that also uses higher line-to-line voltages). The neutral is typically bonded to earth at the service equipment, giving a reference point, but its primary role is to carry current back to the source, not to carry fault currents.

The safety ground is a separate conductor intended to carry fault current only and to help trip protective devices; it is not part of the normal current path. That’s why the neutral’s job isn’t described as “an alternative to grounding” or as something that works primarily with the safety ground.