Here's why:

* Purpose: Ground wires are designed to provide a safe path for electricity to flow to the earth in case of a fault or short circuit.

* Normal Operation: Under normal conditions, there is no current flowing through a ground wire. It's like a safety net that only becomes active in an emergency.

* Safety: If a fault occurs (e.g., a live wire touches a metal casing), the current will flow through the ground wire to the earth, preventing electric shock to people or damage to equipment.

Let me know if you have any other questions!