Which device is used to step down 480V to 120V in this setup?

Which device is used to step down 480V to 120V in this setup?

• A. A transformer
• B. A rectifier
• C. A capacitor
• D. A switch

Answer: (A)

Transformers change AC voltages by magnetic induction between primary and secondary windings. The secondary voltage is proportional to the turns ratio of the windings, so to go from 480V on the primary to 120V on the secondary you need a 4:1 ratio. This device steps down the voltage while allowing the power to be transferred, with the secondary current increasing roughly in proportion to maintain the same power level (minus losses). A rectifier would convert AC to DC, not reduce AC voltage. A capacitor stores energy or smooths voltage, not set a voltage level. A switch simply opens or closes a circuit. So the device used to step down 480V to 120V is a transformer.

Transformers change AC voltages by magnetic induction between primary and secondary windings. The secondary voltage is proportional to the turns ratio of the windings, so to go from 480V on the primary to 120V on the secondary you need a 4:1 ratio. This device steps down the voltage while allowing the power to be transferred, with the secondary current increasing roughly in proportion to maintain the same power level (minus losses). A rectifier would convert AC to DC, not reduce AC voltage. A capacitor stores energy or smooths voltage, not set a voltage level. A switch simply opens or closes a circuit. So the device used to step down 480V to 120V is a transformer.