Cathodic Protection Tester Practice Exam

In the Wenner 4-pin method, which measured value is used to calculate resistivity?

1. Voltage

2. Capacitance

3. Inductance

4. Resistance

The correct answer is: Resistance

The correct answer is that resistance is used to calculate resistivity using the Wenner 4-pin method. In this method, a specific arrangement of four electrodes is employed to measure the resistance of the soil or the material being tested. When the current is passed through the outer electrodes, the resulting voltage is measured across the inner electrodes. From these measurements, the resistance can be calculated using Ohm's Law (R = V/I, where R is resistance, V is voltage, and I is current). Once the resistance is determined, resistivity can be calculated using the geometric factors associated with the configuration of the electrodes, typically involving the distance between them. Resistivity is a key parameter in assessing the effectiveness of cathodic protection systems, as it influences the current distribution and corrosion rates in the targeted structures. Unlike the other concepts like capacitance or inductance, which pertain to different electrical properties and do not link directly to resistivity measurements in this context, resistance directly relates to the measurement performed in the Wenner method.