What is the maximum resistance to ground for rod, pipe, and plate electrodes?

• A. 10 ohms
• B. 15 ohms
• C. 25 ohms
• D. 30 ohms

Answer: (C)

The maximum resistance to ground for rod, pipe, and plate electrodes is typically established to ensure effective grounding in electrical systems, which is vital for safety and performance. A resistance value of 25 ohms is widely accepted in industry standards, such as those set by the National Electrical Code (NEC) and other relevant electrical safety organizations. This limit helps to ensure that under fault conditions, the grounding system will effectively conduct fault currents safely into the ground, minimizing hazards like electrical shock or fire risks. A resistance of 25 ohms strikes a balance between ensuring adequate earth contact and maintaining practical implementation in various soil conditions, making it a standard requirement for grounding electrodes in commercial and industrial applications.

The other options reflect values that, although relevant in different contexts or for other types of grounding applications, do not align with the established maximum resistance for these specific electrode types, which is why they are not the correct answer.