When using pure tungsten or zirconiated electrodes on AC, what forms at the tip of the electrode?

• A. A hemispherical ball
• B. A sharp chisel point
• C. A flat tip
• D. A spiral tip

Answer: (A)

A hemispherical ball forms at the tip. When using pure tungsten or zirconiated electrodes on alternating current, the electrode tip is repeatedly heated in both half-cycles. Molten tungsten has strong surface tension, so the tip tends to round off into a ball rather than stay sharp. This ball shape helps keep the arc stable on AC and avoids the tip wear that would come from trying to maintain a sharp point. Sharp chisel points are more typical for DC welding, while flat or spiral tips aren’t standard outcomes for AC with these electrodes.