How does an ammeter obtain its power feeds?

An ammeter obtains its power feeds primarily from the secondary side of a current transformer (CT). Current transformers are used to step down high currents to a lower level, which can be safely measured by the ammeter. The ammeter measures the output from the CT, where the current is transformed to a proportional value that can be easily read and displayed.

When dealing with high currents, using a CT is beneficial because it allows the connection of the ammeter without interrupting the power circuit. The secondary side of the CT provides the necessary electrical signal proportional to the current flowing through the primary circuit, enabling accurate measurement.

The other options do not accurately describe how an ammeter gets its power feeds. For example, drawing power from the primary side of a transformer would not provide the necessary safeguards for measurement, while a direct battery connection is not how an ammeter operates in typical scenarios involving AC measurements. Similarly, connecting directly to line voltage is also unsafe and not suitable for measuring current. Therefore, the correct approach for ammeters in practical applications is to utilize the secondary side of a current transformer.