Which process concentrates heating at predetermined points?

• A. Projection Welding
• B. Upset Welding
• C. Flash Welding
• D. Arc Welding

Answer: (A)

Concentrated heating at predetermined points happens when the design creates tiny, high-resistance spots where most of the current flows. In projection welding, raised features or projections on the workpieces or electrodes form small contact areas. When current passes through, those projections carry the bulk of the current, so the electrical resistance there is high and heating is concentrated right at those points. The surrounding areas have a larger contact area, so they heat much less and don’t weld, letting you form welds exactly where the projections are.

This is why projection welding is the best fit for producing multiple welds at specific locations in a single pass. Other methods heat differently: upset welding and flash welding generate heat along a seam or at ends of the joint rather than at predefined points, and arc welding heats where the electric arc is located rather than at predetermined feature points on the pieces.