Instrument identification in measurements: An ohmmeter is specifically used to measure which electrical quantity in a circuit or component?

Introduction / Context:
Selecting the correct instrument for measurement prevents errors and damage. An ohmmeter (often part of a multimeter) measures resistance, which is vital for checking components, continuity, and diagnosing open or short faults in wiring and PCB traces.

Given Data / Assumptions:

• Ohmmeters are used on de-energized circuits for accurate resistance readings.

Concept / Approach:
Ohm's law and resistance measurement rely on applying a small known current or voltage and observing the corresponding voltage or current to calculate resistance: R = V / I. A dedicated ohmmeter automates this and displays the resistance directly in ohms (Ω), kilohms (kΩ), or megohms (MΩ).

Step-by-Step Reasoning:

Verification / Alternative check:
Device manuals and symbols: the Ω symbol on a multimeter denotes the resistance function. Continuity mode is related, sounding a tone for very low resistance paths.

Why Other Options Are Wrong:

• Current and voltage require ammeter and voltmeter settings, respectively.
• Wattage (power) is not measured directly by an ohmmeter; power is computed from voltage and current (P = V * I).

Common Pitfalls:

• Measuring resistance on a live circuit can damage the meter or produce false readings due to external sources.

Final Answer:
resistance