Final answer:
Technician B is correct; modern vehicles typically use alternators as the charging unit. An individual lead-acid cell in a car battery has an emf of 2.0 V, and ampere-hours relate to the battery charge capacity and its energy content.
Step-by-step explanation:
The question pertains to the electrical systems in vehicles, specifically charging units used to maintain the battery's charge. Technician A states that many vehicles use an AC generator as the charging unit, while Technician B claims that all vehicles use an alternator as the charging unit. In reality, modern vehicles predominantly use alternators, not AC generators, due to their efficiency and reliability in converting mechanical energy into electrical energy to charge the battery and power the vehicle's electrical systems while the engine is running. However, some older or specialized vehicles may still use AC generators.
The electromotive force (emf) of an individual lead-acid cell in a standard automobile battery is 2.0 V since six cells connected in series provide a total emf of 12.0 V. Ampere-hours (Ah) correspond to the charge capacity of the battery and are directly related to the energy content, as energy in watt-hours can be calculated by multiplying the Ah rating by the nominal voltage of the battery.