Final answer:
The output of an arc welding machine is commonly expressed in terms of Amperage, which refers to the current flowing through the machine and is measured in Amperes (A).
Step-by-step explanation:
The output of an arc welding machine is commonly expressed in terms of Amperage. Amperage refers to the current flowing through the machine and is measured in Amperes (A). The higher the Amperage, the more heat and power the machine can produce.