Which device converts direct current to alternating current?

• A. Rectifier
• B. Transformer
• C. DC-DC Converter
• D. Inverter

Answer: (D)

Converting direct current to alternating current is the job of an inverter, which uses switched electronics to turn a steady DC input into a varying AC output. It typically chops the DC and recreates it as a waveform that alternates polarity, so devices that expect mains-style AC can run from a battery or other DC source.

Rectifiers do the opposite: they take AC and produce DC, often with smoothing. A transformer changes voltage levels but only with AC input, so it cannot convert DC to AC. A DC-DC converter stays in the DC realm, changing one DC voltage to another without creating AC.

Inverters are used for battery backups, solar power systems, and any situation where a DC source needs to power AC appliances.