Final answer:
The correct answer is option b. Voltage-amperage. AC welding equipment utilizes transformers to step down the voltage and boost the amperage for welding.
Step-by-step explanation:
AC welding machines house transformers to reduce input voltage and increase output amperage for safe and effective welding. The correct answer is option b. Voltage-amperage. Transformers in AC welding machines are crucial for adjusting electrical current characteristics to suitable levels for welding processes. A step-down transformer is used to decrease the high voltage from the power lines (usually available in hundreds to thousands of volts) to a much safer level (around 110 or 220 V). At the same time, the transformer increases the current (measured in amperes), which provides the energy needed for the welding arc. Assuming the transformer is highly efficient, often more than 99%, the power output is almost equal to the power input, following the principle Pp = IpVp = IsVs = Ps, where P stands for power, I for current, V for voltage, and the subscripts p and s indicate primary and secondary coils of the transformer, respectively.