Discussion
In DC welding, straight polarity is recommended for which of following case?
Answer: B
The keyed answer is welding with light coated electrodes.
With straight polarity the electrode is negative and the work is positive, so more of the arc heat goes into the work and the electrode melts more slowly. In the trade-school convention this paper follows, bare and lightly coated electrodes are run on straight polarity, while heavy coatings are paired with reverse polarity.
Heavy and super heavy coated electrodes, and sheet metal work where deep penetration would burn through, are the cases the convention assigns to the other arrangement. Polarity in practice depends on the electrode class and the maker's data sheet, so this item is a textbook rule rather than a universal one.
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