Recreational Vehicle (RV) Technician Practice Test

What is a primary difference between 120v DC and 12v DC wiring?

1. Solid wire versus stranded wire

2. Plastic insulation versus rubber insulation

3. Color coding of wires

4. Gauge size

The correct answer is: Solid wire versus stranded wire

The primary difference between 120v DC and 12v DC wiring relates to the gauge size of the wire used for each voltage level. Higher voltage systems, such as 120v DC, typically require thicker wire (lower gauge number) to handle the higher current without overheating. This means that for the same amount of power transmission, 120v wiring will generally use a gauge that is larger than that used for 12v systems. In contrast, 12v DC wiring generally uses thinner wire (higher gauge number) because it carries less current. The wire's ability to handle electrical load is determined primarily by its gauge, which impacts factors like resistance and heat generation. While solid versus stranded wire, plastic versus rubber insulation, and color coding of wires may have their own importance in certain applications or standards, they do not represent the fundamental difference in the context of voltage levels between 120v DC and 12v DC systems. The choice of wire gauge is crucial for safely and effectively managing the electrical load for the specific voltage used.