What is the primary difference between AC and DC in welding?

The primary difference between AC and DC in welding is that AC, or alternating current, changes direction periodically. This means that the current flows in one direction for a certain period and then reverses to flow in the opposite direction. This characteristic of AC is important in particular welding applications, such as TIG (Tungsten Inert Gas) welding, where the alternating nature helps to clean the metal surface by removing impurities through the oscillation of the current.

In contrast, DC, or direct current, flows continuously in one direction. Each type of current has its specific uses and advantages, but the defining feature of AC is its alternating nature, which is fundamental to its application in various welding processes.

The other options do not accurately describe the characteristics of AC and DC. For instance, DC does not flow in multiple directions; it is known for its steady flow in one direction. While AC is versatile and can be used for various materials, including non-ferrous metals, the statement about AC being used for carbon steel only is misleading. Additionally, while the nature of DC may lead to specific welding challenges such as porosity under certain conditions, it is not a fundamental property of DC itself. Thus, the fundamental understanding of AC's alternating nature is key for