ERW is a group of processes in which heat produced by resistance to the flow of current is used to join metals that are held under pressure. Which statement expresses this principle correctly?

• A. ERW is a group of processes in which heat produced by resistance to the flow of current is used to join metals that are held under pressure
• B. ERW uses external heat sources and filler metal to join metals
• C. ERW relies on arc heating with shielding gas
• D. ERW uses soldering techniques to join metals

Answer: (A)

ERW relies on heat generated by electrical resistance as current flows through the metal, with the pieces held together under pressure so the heated surfaces fuse. This exactly describes the process: the heat comes from the current’s resistance, and pressure brings the metal surfaces into contact to form the weld without adding filler metal. The other statements describe different welding methods that use external heat, arc heat with shielding gas, or soldering, none of which capture the essential idea of ERW.