Final answer:
In direct current electrode negative (DEN) welding, the greatest amount of heat is produced in the base metal, as this is where the resistance to current flow is greatest. The electrode in DEN acts as a cathode, but its role in heat production is lesser compared to the base metal.
Step-by-step explanation:
The question pertains to welding, specifically the heat effects of direct current electrode negative (DEN) in the process. In DEN welding, the greatest amount of heat is generated at the point where the resistance to the flow of current is the greatest. This typically is the base metal, as the electrons flow from the electrode to the workpiece, causing more resistive heating in the workpiece rather than in the electrode, welding machine, or shielding gas.
When using DEN, the electrode becomes the negative pole, also known as the cathode. However, the brief on the cathode being the positive electrode and increasing in mass due to the reduction and copper metal production refers to electrochemistry, which is different from the concept applied in welding processes. In the context of welding, the polarity of the electrode and the heat distribution concern the direction of current flow and the resistance encountered, which determines where the heat is concentrated.