What is the primary purpose of ammeters in aircraft electrical systems?

• A. To monitor voltage
• B. To monitor current
• C. To monitor resistance
• D. To monitor frequency

Answer: (B)

Measuring current flow is the main purpose. The ammeter shows how much current is being drawn from or supplied to the aircraft’s electrical system. This is critical because excessive current can indicate an overload or a short, which can damage components or trip protective devices. It also lets you verify the charging system is working properly—whether the generator or alternator is delivering current to the bus, or whether the battery is discharging to supply power.

The instrument is wired in series with the circuit (often via a low-resistance shunt) so all current passes through it with minimal voltage loss and accurate reading. Many ammeters also indicate direction, showing charging versus discharging, which helps assess the health of the electrical system during operation.