Which polarity is used to help prevent arc blow during welding?

• A. DC polarity
• B. AC polarity
• C. Pulsed DC
• D. No polarity required

Answer: (B)

Arc blow happens when the magnetic field generated by the welding current interacts with surrounding ferromagnetic material and pushes or pulls the arc sideways. If the current runs in one direction continuously, that magnetic field stays the same and a steady deflection can develop, causing the arc to wander.

Using alternating current changes the game. The polarity flips each half cycle, so the magnetic field also reverses repeatedly. Those rapid reversals cancel out the steady sideways force, letting the arc stay centered over the joint instead of being blown off course. This is especially helpful when welding near magnetic fields, corners, or thick pieces where arc blow is more likely.

Pulsed DC and fixed DC polarity don’t provide the same, complete cancellation of the deflecting magnetic forces. No polarity defined at all isn’t applicable to welding processes, where polarity is a fundamental control.

So, AC polarity is used to help prevent arc blow.