What best describes the heat generation in resistance spot welding?

• A. Electrical resistance between sheets under pressure
• B. Inductive heating from coil
• C. Friction heating
• D. Radiant heating from arc

Answer: (A)

Heat generation in resistance spot welding comes from electrical resistance at the interface of the sheets under applied pressure. When a high current passes through the metal during welding, power is dissipated as heat (P = I^2R). The heat concentrates where the sheets contact each other, especially at the point under the electrodes, because that is where contact resistance is highest and the current density is highest. This localized heating softens and melts the metal to form a weld nugget that cools into a strong joint. The electrode pressure helps maintain contact and localize heating, while the coil, friction, or arc heating methods aren’t how this process generates heat.