When testing an electrical circuit for current flow, which instrument would be most appropriate?

The ammeter is the most appropriate instrument when testing an electrical circuit for current flow because it is specifically designed to measure the amount of electric current flowing through a circuit in amperes. To obtain an accurate reading, the ammeter must be connected in series with the circuit components, allowing it to measure the flow of current directly.

In contrast, other instruments such as the voltmeter are used primarily to measure voltage across components rather than current. A wattmeter measures electrical power, which is a product of both voltage and current, but does not provide a direct measurement of current by itself. The frequency meter is utilized to measure the frequency of alternating current signals and does not relate to current flow measurements. Thus, for determining current flow directly in a circuit, the ammeter is the targeted choice.