Which polarity requires the tungsten electrode to be connected to the negative pole?

The correct answer pertains to Direct Current Electrode Negative (DCEN), which is a polarity configuration in gas tungsten arc welding (GTAW). In this setup, the tungsten electrode is connected to the negative terminal of the power supply. This configuration allows for better heat concentration at the workpiece since approximately 70% of the heat generated in the welding arc is directed towards the workpiece, improving penetration and stability in the arc.

DCEN is particularly advantageous when welding materials that require precise control over heat input, such as thin sections of metal or when working with materials like aluminum in certain conditions. By having the tungsten electrode negative, it also minimizes the amount of electrode wear, enhancing the lifespan of the tungsten.

The other options represent different polarities. Direct Current Electrode Positive (DCEP) involves the electrode being connected to the positive terminal, which favors surface cleaning for materials like aluminum but can lead to faster wear of the tungsten. Alternating Current (AC) typically alternates between positive and negative, providing a balance of benefits for various applications but does not involve a fixed connection of the electrode to either terminal. Understanding these distinct polarities is crucial for selecting the appropriate welding technique based on the materials and conditions.