Failure modes of resistors: When a fixed resistor overheats and fails, does it typically fail as a short-circuit path or as an open circuit? Choose the accurate statement about common real-world behavior.

Introduction / Context:
Diagnosing faults quickly requires knowing typical failure modes. Fixed resistors subjected to excessive power dissipation (heat) usually fracture, crack, or the resistive film breaks, interrupting current flow. Understanding this behavior helps technicians decide where to place the meter probes and what values to expect when equipment fails.

Given Data / Assumptions:

• Component type: fixed carbon film, metal film, or wirewound resistors.
• Stress: over-power, prolonged overheating, or surge events.
• No exotic fusible or specially constructed parts designed to fail short.

Concept / Approach:
Resistors rely on a continuous resistive path. Thermal overstress tends to break or vaporize that path, producing an open circuit (very high resistance). While some rare failure mechanisms can lead to partial shorts (especially with contaminants or carbonization), the overwhelmingly common outcome for standard resistors is an open circuit.

Step-by-Step Solution:

Verification / Alternative check:
Field experience: ohmmeter readings on burned resistors trend to very high resistance or infinity. Service manuals often advise checking for opens in suspect resistors after visible scorching.

Why Other Options Are Wrong:

• They usually short: Uncommon for standard parts; shorts are more associated with semiconductors failing catastrophically.
• Depends on color code: Color code labels value/tolerance, not failure mode.
• Always perfect conductor/insulator: Real failures vary; “open” means very high resistance, not ideal infinity.

Common Pitfalls:
Assuming any burnt part is shorted; overlooking that some resistors are intentionally fusible and act like fuses (open by design).

Final Answer:
Correct — they commonly go open when burned