Electric current — Describe

How are ammeters used in a circuit, and what is meant by their having different ranges?

An ammeter is connected in series in the circuit so that all the current to be measured passes through it, and it has a very low (near-zero) resistance so it does not affect the size of the current. Ammeters may be analogue (pointer and scale) or digital (numerical display), and are available with different ranges (e.g. 0-1 A or 0-5 A) so an appropriate range can be selected to measure currents of different sizes accurately.