NEC Commercial Electrical Practice Test

What material is typically used for grounding electrodes in underground applications?

1. Plastic pipe

2. Non-metallic cable

3. Metal underground water pipe

4. Conduit

The correct answer is: Metal underground water pipe

In underground applications, the use of metal underground water pipes as grounding electrodes is based on their conductivity and established standards in electrical codes. Metal pipes, such as those made from copper or steel, provide a low-resistance path for ground fault currents, which is essential for safety and protection against electrical hazards. The National Electrical Code (NEC) recognizes metal water pipes as effective grounding electrodes because they are often in direct contact with the earth and can facilitate efficient grounding connections. They help in dissipating electrical energy into the ground, thus enhancing the electrical safety of installations by minimizing the risk of shock or fire. While other materials like plastic pipes and non-metallic cables do not conduct electricity and are therefore not suitable for grounding purposes, conduits can be used for specific electrical applications but typically don't serve as a primary grounding electrode on their own. In summary, metal underground water pipes are favored for their conductive properties and reliable connection to the ground in underground settings.