Resistor Failure: Is it Open or Short Circuit?

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Discussion Overview

The discussion revolves around the failure modes of resistors, specifically whether a failed resistor typically results in an open circuit or a short circuit. Participants explore the implications of resistor failure in terms of resistance values and circuit behavior.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants assert that a resistor typically fails open, leading to infinite resistance and no current flow.
  • Others question whether a failed resistor can be defined as having zero resistance, suggesting that this would imply a short circuit.
  • One participant defines a failed resistor as one that does not meet its rated resistance, which could mean either too high or too low resistance.
  • A participant mentions that resistors have tolerance ratings, and exceeding these ratings indicates failure, impacting reliability in circuits.
  • Another participant notes that excessive heat from current can cause a resistor to fuse open, reinforcing the idea of open circuit failure.

Areas of Agreement / Disagreement

Participants express differing views on the nature of resistor failure, with some supporting the idea of open circuit failure while others raise the possibility of short circuit conditions. The discussion remains unresolved regarding the definitive failure mode of resistors.

Contextual Notes

There are nuances regarding the definitions of failure, resistance values, and tolerance ratings that are not fully resolved in the discussion.

asdf1
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The statement, "when a resistor fails, it will normally open." is true.
But I don't understand:
when a resistor fails, doesn't that mean that the resistor doesn't work? so doesn't that mean that resistance=0=short circuit?
 
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If a resistor burns out so that the counductive material is disrupted, then it is an open circuit with infinite resistance, i.e. conductance = 0.

If somehow, the resistor short circuits then it has no resistance (and it is then no longer a resistor).
 
Last edited:
is a failed resistor one that has 0 resistance?
 
A resistor is "failed" when it doesn't provide the amount of resistance it is rated to, whether it be too much or too little.
 
FredGarvin said:
A resistor is "failed" when it doesn't provide the amount of resistance it is rated to, whether it be too much or too little.
That's a good point. Perhaps I can expand on that..
Resistors are given a tolerance rating, which could be within 1%, 2%, 5%, or 10% of its nominal value. (You will see what I mean by following the link). If your resistor has a tolerance of 1% and it now measure more than that, it fails to meet its specification. Its a bad part and cannot be trusted to hold even its present measured value in a circuit.

asdf1 said, "when a resistor fails, it will normally open" . A resistor normally heats up as it conducts current. If the resistor is weakened or defective, that heat can cause the resistor to fuse open. Just like a real fuse, the resistor becomes an open circuit.
 
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i see! thanks! :)
 

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