Which welding process uses electrical resistance to join two metal sheets by clamping them together?

• A. MIG Welding
• B. Resistance Spot Welding (RSW)
• C. TIG Welding
• D. Ultrasonic Welding

Answer: (B)

This question focuses on welding methods that generate heat through electrical resistance while the sheets are squeezed together. Resistance Spot Welding uses two metal sheets pressed between electrodes while a high current passes through them. The contact points between the sheets experience electrical resistance, which converts electrical energy into heat, melting and fusing the metal right at the interface. The clamping pressure and rapid heating make a strong, localized weld very quickly, which is why this method is widely used for automotive body panels and other thin sheet metal.

MIG welding, by contrast, melts metal with an arc created by a consumable filler wire and shielding gas, not by resistance heating at the contact surface. TIG welding relies on a separate arc with a non-consumable tungsten electrode and shielding gas, also not based on resistance heating between clamped sheets. Ultrasonic welding uses high-frequency vibrations to generate heat by friction at the interface, which is a different heating mechanism and is commonly used for plastics and certain thin metals rather than relying on electrical resistance to weld large metal sheets.