Nate Core Practice Test

What might cause a voltage drop across a set of closed contacts?

1. Pitting or dirt

2. High resistance

3. Overload in the circuit

4. Short circuit

The correct answer is: Pitting or dirt

A voltage drop across a set of closed contacts can occur due to pitting or dirt on the contacts. When electrical contacts experience arcing or wear, they can develop small pits on their surfaces. These imperfections disrupt the smooth flow of electricity, leading to increased resistance at the contact point. Dirt or contamination on the contacts can further exacerbate this issue, creating a barrier that prevents optimal current flow. As a result, the voltage across the contacts decreases, which can negatively affect the performance of the circuit. In contrast, high resistance can also lead to a voltage drop; however, the specific mention of pitting or dirt particularly highlights a direct cause related to contact integrity. Overload in the circuit typically results in excessive current rather than a localized voltage drop at the contacts themselves. While a short circuit is characterized by a drastic reduction in resistance, it does not directly cause a voltage drop across closed contacts; in fact, it generally leads to more severe problems within the circuit. Therefore, the phenomenon of contact deterioration due to pitting or dirt offers a clear and focused explanation for the observed voltage drop.