Certified Welding Inspector Practice Exam

Which type of current is utilized in automatic arc welding?

1. Direct current only

2. Alternating current only

3. Both direct and alternating current

4. High frequency current only

The correct answer is: Both direct and alternating current

Automatic arc welding can utilize both direct current (DC) and alternating current (AC) depending on the specific welding process and the materials being joined. Each type of current has its own characteristics that can optimize the welding process. Direct current is commonly used because it provides a more stable arc and better control, which is crucial for many welding applications. It is particularly advantageous when working with ferrous metals, as it can produce a smoother weld bead and reduce spatter. On the other hand, alternating current is often used for welding non-ferrous metals and certain joint configurations. In processes such as TIG (Tungsten Inert Gas) welding, AC is beneficial for cleaning the oxide layer on aluminum, ensuring better penetration and a higher quality weld. Automatic welding systems can be designed to switch between AC and DC modes depending on the requirements of the operation, making them versatile and capable of handling a wide range of materials and thicknesses. Thus, both AC and DC play critical roles in automatic arc welding processes, which justifies the selection of the answer that acknowledges both types of current.