DCEN is impractical with GMAW because which factor is true?

• A. Shielding gas incompatible
• B. Penetration decreases uniformly
• C. Melting rates are unequal for each half-cycle
• D. Increases spatter

Answer: (C)

In GMAW, how heat is shared between the electrode and the weld pool depends on the current waveform and polarity. When the electrode is negative, the arc heat distribution and metal transfer become tied to the current’s half-cycles. In alternating current, each half-cycle reverses polarity, so the electrode and the weld pool experience different melting intensities in each half-cycle. That results in unequal melting rates from one half-cycle to the other. DCEN lacks that balancing action, so you’d have a fixed, imbalanced melting behavior, making stable, controllable metal transfer difficult. That is why the idea that melting rates are unequal for each half-cycle best explains why DCEN is impractical for GMAW. The other factors—shielding gas compatibility, uniform penetration, or increased spatter—are not the primary limiting reason here.