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SarkariResultOutBMS · 2024

Previous Year Question

As per National Electrical Code for a grounding electrode conductor, the maximum resistance of grounding electrode (single rod, pipe or plate) to earth must not exceed
  1. 100 ohms
  2. 50 ohms
  3. 25 ohms
  4. 60 ohms

Correct answer: C

Explanation

The code requirement cited by the question limits the resistance of a single rod, pipe or plate grounding electrode to the specified maximum value. The value matching that requirement is option C.

Formula

Electrode resistance must not exceed the code limit stated for the electrode arrangement

Step-by-step solution

Maximum Electrode Resistance explanatory diagram

Correct Answer

C — 25 ohms

Concept and Reasoning

The code requirement cited by the question limits the resistance of a single rod, pipe or plate grounding electrode to the specified maximum value. The value matching that requirement is option C.

Calculation / Key Relation

Electrode resistance must not exceed the code limit stated for the electrode arrangement

Exam Takeaway

For code questions, distinguish a single-electrode limit from system-design targets for special installations.

Common Mistake

Do not substitute a preferred engineering target for the explicit code limit asked in the question.

Common mistake

Do not substitute a preferred engineering target for the explicit code limit asked in the question.

Exam tip

For code questions, distinguish a single-electrode limit from system-design targets for special installations.

Quick method

For code questions, distinguish a single-electrode limit from system-design targets for special installations.