Which appliance converts 12-volt direct current from a vehicle's electrical system to 110-volt alternating current?

The appliance that converts 12-volt direct current (DC) from a vehicle's electrical system to 110-volt alternating current (AC) is an inverter. An inverter takes the low voltage DC power and transforms it into higher voltage AC power, which is often required for running household appliances or equipment designed to work off standard electrical outlets.

Inverters are commonly used in situations where you need to operate devices that are not designed to work with the vehicle’s low voltage system. This is particularly useful in emergency services, such as fire trucks or ambulances, where AC-powered tools and equipment may need to be utilized on-site.

While generators are capable of producing AC current, they do so by directly converting mechanical energy into electrical energy, rather than converting an existing DC source. Rectifiers are used to convert AC current to DC, serving a different purpose altogether, and converters typically refer to devices that may change one form of DC to another (such as stepping up or down voltages) without involving AC current. Thus, the inverter is the specific device designed for the function described in the question.