Q1: Projection welding & stud welding is categorised as the __________ welding.

ANS:C - resistance

Projection welding and stud welding are categorized as resistance welding. Resistance welding is a group of welding processes that use the heat generated by the resistance to electric current flowing through the workpieces to join them together. In these processes, the workpieces are clamped together and subjected to pressure while an electric current is passed through them. The resistance to the current flow generates heat at the interface between the workpieces, causing them to melt and fuse together. Projection welding is a type of resistance welding where raised or contoured areas on one or both of the workpieces, known as projections, concentrate the current flow and heat generation, resulting in localized melting and welding. Stud welding is another variation of resistance welding where a specially designed fastener, known as a stud, is welded onto a workpiece, typically a metal plate or sheet. Therefore, projection welding and stud welding are both examples of resistance welding processes.