Final answer:
An ohmmeter is the meter that uses its own internal power source to measure resistance in a load or circuit by applying Ohm's law.
Step-by-step explanation:
The meter that must use its internal power to check a load or circuit is the ohmmeter. Unlike ammeters and voltmeters that only need to be placed in series (for ammeters) or in parallel (for voltmeters) with the circuit to measure current and voltage respectively, an ohmmeter operates differently. An ohmmeter must supply a known voltage or current to measure resistance using Ohm's law, which relates current (I), voltage (V), and resistance (R) as R = V/I. Since an ohmmeter uses its own power source, typically a battery, it can test the resistance of the component by providing the necessary current for the measurement.