Cathodic Protection Tester Practice Exam

In terms of cathodic protection testing, what does the term 'IR drop' refer to?

1. Current loss in the soil

2. Voltage drop across a resistance

3. Measurement of magnetic field

4. Interference from environmental factors

The correct answer is: Voltage drop across a resistance

The term 'IR drop' in cathodic protection testing specifically refers to the voltage drop across a resistance, which is calculated using Ohm's Law (Voltage = Current x Resistance). This concept is crucial in cathodic protection systems because it helps in understanding how much voltage is actually available at the structure being protected. When measuring the potential of a cathodic protection system, if there is a significant IR drop, it can lead to inaccuracies in potential readings. This means that while the supplied current may be sufficient for cathodic protection, the voltage measured at the structure may not reflect the true protection level due to resistance in the soil or other materials. Understanding IR drop allows for proper adjustments and accurate assessment of how effective the cathodic protection system is at mitigating corrosion on metal surfaces. In this context, current loss in the soil and interference from environmental factors might affect how current is distributed or how readings are interpreted, but they do not directly define the concept of IR drop. Measurement of magnetic field is unrelated to IR drop, as it involves different electrical principles altogether. Hence, focusing on the voltage drop across resistance gives a clear and direct understanding of one of the critical aspects of cathodic protection evaluations.