Grounding misconceptions identified
How many times have we heard, ‘current follows the path of least resistance” and “a good ground rod will clear fault”? Plenty I am sure. And although these popular notions have an intuitive quality about them, they are only partly based on fact. And the part of the statements that aren’t totally based on fact can have very practical implications and should not be taken for granted.
Oftentimes, people compare current flow to water flow for purposes of illustration. Water doesn’t flow over a rock if it can get around it. Therefore, individuals believe that this same theory holds true for current – current will follow the path of least resistance and divert from higher resistance.
This could not be farther from the truth. The laws of parallel resistances reveals a more complex reality that tells us that voltage will pull current through ALL available paths in the amounts equal with the opposing force of resistance. If two parallel resistances are more or less equalized the result can be lethal.
So focusing on only the obvious current path can leave dangerous parallel circuits unnoticed and unattended. Unknown parallel paths are often overlooked where grounding systems are involved (they can be found in neighboring buildings) posing a potential danger to all who come in contact with it. It is common to have several amps of current flowing on a ground rod or other parts of the grounding system. It is good practice to check a grounding system with a clamp-on ammeter before making contact with it to ensure safety.