Red Seal Welder Practice Exam

How do AC and DC welding currents differ?

1. AC has a higher voltage than DC

2. DC flows in one direction, while AC switches polarity

3. AC is used only for aluminum welding

4. DC can only be used in automatic welding processes

The correct answer is: DC flows in one direction, while AC switches polarity

The distinction between AC (Alternating Current) and DC (Direct Current) welding currents primarily revolves around the direction in which the electrical current flows. In a DC system, the electrical current flows continuously in one direction. This provides a stable arc and is generally better for welding processes that require a more consistent and controlled heat output. This stability also makes DC current more suited for various materials, including steel and stainless steel. In contrast, AC welding current alternates direction, meaning it switches polarity periodically. This characteristic can be beneficial for certain welding applications, such as with aluminum, because it can help in cleaning the oxide layer from the surface of the aluminum as the current polarity changes. This alternating nature allows for improved penetration and a better overall quality in the weld. The other options present notions that do not accurately capture the fundamental differences between AC and DC currents. For instance, while it is true that AC can be advantageous in specific applications, saying that AC has a higher voltage than DC is misleading since voltage levels typically depend on the specific welding setup rather than the type of current. Additionally, limiting AC to aluminum welding ignores its versatility, and implying that DC can only be used in automatic welding processes does not reflect the reality that DC is widely utilized in manual welding