Cathodic Protection Tester Practice Exam

In the equation for resistivity in the Wenner 4-pin method, what does 'R' represent?

1. Resistance in volts

2. Resistance in ohms

3. Resistance in milliamps

4. Resistance in amperes

The correct answer is: Resistance in ohms

In the Wenner 4-pin method, 'R' represents the resistance measured across two of the four electrodes used in the setup. This resistance is quantified in ohms, which is the standard unit of measurement for electrical resistance in the International System of Units (SI). The Wenner method involves injecting a known current through two outer electrodes and measuring the resulting voltage drop across the two inner electrodes. Ohm's law, which states that voltage (V) is equal to the product of current (I) and resistance (R), is applied here. Since 'R' is derived from this relationship, it is inherently expressed in ohms. Understanding resistivity is essential in cathodic protection testing because it influences the effectiveness of the protection system. The measured resistance helps in calculating the resistivity of the soil or medium, which is critical for designing cathodic protection systems effectively.