How is an ammeter usually connected to a circuit under test?

An ammeter is designed to measure the flow of electrical current (amperes) through a specific path. To accurately count the electrons flowing through that path, the ammeter must become part of the circuit itself, meaning it must be connected in series. Because all the current in that branch must pass through the meter, ammeters are built with exceptionally low internal resistance. This prevents the meter from acting as a bottleneck and restricting the very current it is trying to measure. Connecting an ammeter in parallel across a voltage source or component is highly dangerous. Because of its near-zero resistance, it will create a short circuit, drawing a massive amount of current that will instantly blow the meter's fuse or destroy the device.