If travel speed increases while amperage and voltage stay the same, what happens to heat input?

• A. Increase
• B. Stay the same
• C. Vary unpredictably
• D. Decrease

Answer: (D)

Heat input is the energy delivered to the weld per unit length. The arc power is V × I, which stays the same if voltage and amperage are constant. Increasing travel speed means this same power is spread over a longer length in the same time, so the energy per unit length drops. In formula terms, heat input per unit length is proportional to (V × I) / travel speed. Therefore, when travel speed rises while voltage and amperage remain fixed, heat input decreases.