What last numbers of the electrodes can run on both Direct Current Positive (DC+) and Alternating Current (AC)?

The correct answer is based on the electrical characteristics of welding electrodes. The last numbers that denote electrodes capable of functioning effectively with both Direct Current Positive (DC+) and Alternating Current (AC) are indeed those that can handle a variety of welding conditions. In the context of the various classifications provided within the AWS A5.1 standard, the electrodes ending in 8, 6, and 1 are specifically designed for versatility, making them suitable for multiple current types.

Electrodes classified with the last digits of 8 signify capability for both DC+ and AC, thus making them ideal for applications requiring different power sources. Similarly, those ending in 6 and 1 also possess this dual functionality, enjoying widespread usage in varied welding environments. This adaptability to different current types ensures that welders have the flexibility in material and technique, enhancing quality and efficiency in the welding process.

The other choices do not contain numbers associated with electrodes known for this dual capability. Thus, while they may pertain to specific applications or current types, they do not reflect the required versatility of operation on both DC+ and AC currents. Understanding the significance of these last digits aids welders in selecting the appropriate electrodes for their equipment and project needs.