The amount of electrical energy supplied by a welding arc to a workpiece is called

• A. Voltage
• B. Heat input
• C. Current
• D. Power

Answer: (B)

Heat input is the amount of energy from the welding arc that ends up as heat in the workpiece. The arc delivers electrical energy, and most of that energy is converted into heat in the metal, driving melting and metallurgical changes. Voltage alone describes the driving potential, and current describes how much charge flows, while power is the rate at which energy is delivered (P = V × I). The term that specifically refers to the energy deposited into the metal for welding—often expressed per unit length or per unit weld time—is heat input. In practice, heat input is calculated as voltage × current, adjusted for travel speed, to give energy per inch (or per millimeter) of weld.