AG Mechanics CDE Practice Exam

During welding, which direction does heat move most rapidly in metal?

1. Downward

2. Horizontally

3. Upward

4. Vertically downward

The correct answer is: Downward

During welding, heat moves most rapidly downwards in metal because of gravity. Heat is laterally conducted along the top surface of the metal and is then conducted downwards through the thickness of the metal, creating a temperature gradient. This means that the base of the metal becomes hotter faster than the top surface, leading to heat moving downwards at a more rapid pace. This explains why option D, vertically downward, is incorrect. Heat is also not moving horizontally (option B) or upwards (option C), as those directions do not follow the natural flow of heat in metal. Therefore, the most accurate option is A, downward.