Final answer:
An ammeter is used to measure electric current and should be connected in series with the circuit component. It cannot measure pressure drop, magnetic fields, load in parallel wires, or direct power across loads.
Step-by-step explanation:
An ammeter is an instrument designed to measure the rate of electric current in a circuit. The correct reading that an ammeter can provide is the current flowing through the circuit. Ammeters must be connected in series with the component being measured to accurately assess the current. Unlike voltmeters, which are connected in parallel, ammeters have a low internal resistance to ensure minimal impact on the circuit's total resistance.
For example, if measuring the current flowing through resistors connected in series, a single ammeter is placed in series with the resistors. In parallel circuits, multiple ammeters may be necessary to measure the current through each separate branch. Connecting an ammeter in parallel is a practical error that could damage the instrument due to its low resistance, which would draw most of the current through itself, potentially exceeding its design limits.