A damaged resistor in practical electronics troubleshooting may show which observable or measurable characteristics?

Introduction:
Recognizing signs of resistor failure is essential for effective troubleshooting. Resistors can fail open, drift in value, or show visible damage depending on how they were stressed (overpower, surge, overheating).

Given Data / Assumptions:

• Through-hole or surface-mount resistors in typical low-voltage circuits.
• Possible stressors: overcurrent, overvoltage, thermal cycling, environmental factors.
• Technician has access to visual inspection and an ohmmeter.

Concept / Approach:
Failure modes include visual signs (discoloration, cracking, burn marks) and electrical changes (value drift upward due to film damage or open-circuit). An ohmmeter measurement (with power removed and at least one lead isolated) confirms the suspected change against tolerance.

Step-by-Step Solution:
Power down and discharge nearby capacitors for safety.Inspect: look for scorching, cracking, or lifted pads; these indicate overheating.Measure with an ohmmeter: compare measured value to the color-code/marked value and tolerance.Interpretation: significantly higher-than-nominal or infinite resistance indicates damage; sometimes value decreases due to carbonization paths, but increases/open are common.

Verification / Alternative check:
Cross-check by substituting a known-good resistor of the same value and retesting circuit behavior to confirm that the suspect part was the fault source.

Why Other Options Are Wrong:

• may appear burned: True but not the only indicator.
• may have an increased resistance value: True; drift/open is frequent after overheating.
• may be checked with an ohmmeter: True; standard diagnostic method.
• none of the above: Incorrect because all three are valid indicators.

Common Pitfalls:

• Measuring in-circuit without isolating one lead, causing parallel paths to skew readings.
• Ignoring tolerance and temperature coefficient when judging small deviations.
• Overlooking intermittent faults from hairline cracks that change with flex or heat.

Final Answer:
All of the above