Which polarity has electrons flowing from the tungsten to the work piece?

• A. DC+
• B. DC-
• C. AC
• D. Pulsed DC

Answer: (B)

In welding with direct current, electron flow goes from the negative side to the positive side. When the tungsten electrode is set to negative, it acts as the source of electrons, so they move from the tungsten toward the work piece through the arc. This polarity is often called electrode negative. It concentrates heat into the work piece and helps with penetration, while keeping the tungsten cooler.

If the polarity were positive, electrons would flow from the work piece to the tungsten, reversing the arc’s heat distribution. Alternating current switches direction, so there isn’t a constant single direction of electron flow, and pulsed direct current simply turns the current on and off while maintaining a chosen polarity during the on cycles.