The consequences of resistor failure are diverse, depending on the function of the resistor in the circuit, failure mode, circuit design, and severity of the failure. The following are some of the main consequences, ranging from minor functional abnormalities to severe equipment damage and even safety hazards:
Complete interruption of circuit function (most commonly caused by open circuit failure):
Open circuit: This is one of the most common failure modes of resistors. The internal disconnection of the resistor is equivalent to an infinitely large resistor.
Consequence: Current cannot flow through this branch. This will lead to:
Downstream circuit without power supply: If the resistor is in the power path, the subsequent circuit part cannot receive voltage, and the entire functional module or equipment stops working.
Signal path interruption: If the resistor is in the signal transmission path (such as voltage division, bias, coupling), the signal cannot be transmitted, resulting in functional abnormalities (such as no sound, no image, sensor failure).
Control logic failure: In logic circuits or microcontroller circuits, an open circuit may cause abnormal input/output signals, program crashes or crashes.
Visual faults such as LED not lighting up and motor not rotating.
Abnormal circuit function or performance degradation (most commonly caused by resistance drift or slight changes):
Resistance drift/change: The resistance value deviates from the nominal value (increases or decreases), but is not completely open or short circuited. May be caused by aging, overload, overheating, humidity, voltage stress, or manufacturing defects.
Consequences:
Signal distortion: In analog circuits such as amplifiers and filters, changes in resistance values can alter key parameters such as gain, bandwidth, and cutoff frequency, resulting in sound distortion, image blurring, and decreased measurement accuracy.
Bias point offset: Active devices such as transistors and operational amplifiers require a specific DC operating point (bias). Changes in the voltage divider resistance value can alter the bias voltage/current, causing the device to operate in a nonlinear region, resulting in performance degradation or even cutoff/saturation, causing severe distortion or loss of function.
Inaccurate reference voltage/current: The precise resistance value used to generate reference voltage or set current may cause a decrease in the accuracy of the entire system that relies on this reference (such as ADC/DAC conversion accuracy, regulated power output).
Timing/oscillation frequency change: In RC timing circuits or oscillators, changes in resistance values can alter the time constant or oscillation frequency.
Logic level error: In pull-up/pull-down resistors or level conversion circuits, abnormal resistance values may result in logic high/low levels not meeting specifications, causing digital circuit misoperation or communication errors.
Unstable equipment operation: intermittent faults, parameter drift, intermittent good and bad.
Overcurrent, overheating, and even fire (most commonly caused by abnormal decrease in resistance or partial short circuit):
Abnormal decrease in resistance/partial short circuit: Local conduction occurs inside the resistor, and the resistance value becomes much smaller than the nominal value, but it is not completely short circuited to zero ohms. It may also be caused by physical damage, overvoltage breakdown, or pollution.
Consequences:
Current increase: According to Ohm's law 'I=V/R', a decrease in resistance value R will cause an increase in the current I flowing through.
Resistance overheating itself: power dissipation ` P=I ² R ` or ` P=V ²/R `. An increase in current or an abnormal decrease in resistance can lead to a significant increase in power consumption. Resistors may generate abnormal heat, such as smoking, burning, or discoloration.
Associated damage: Excessive current may exceed the rated value of the power supply or other series connected components (such as fuses, transistors, ICs, PCB wiring), causing them to overheat and damage.
Fire risk: In extreme cases, overheating of resistors or surrounding components may ignite nearby plastics, solder residue, or other flammable materials.
Short circuit (relatively rare but with serious consequences):
Complete short circuit: The resistance value at both ends of the resistor is close to 0 ohms. Usually caused by severe overvoltage breakdown, physical short circuits (such as tin bridges, metal debris), and complete melting of internal structures.
Consequences:
Extremely high current: an almost unrestricted current flowing through the short-circuit point.
Immediately blow the fuse: If there is a fuse in the circuit, it is usually blown immediately to protect the circuit.
Catastrophic damage: If there is no fuse or the fuse is not blown in time:
Power overload damage: The power supply may burn out due to overcurrent.
PCB wiring burnout: High current can burn copper foil wiring.
Series component burnout: Components connected in series with short-circuit resistors (such as drive transistors, ICs) will burn out due to overcurrent.
Potential fire risk: extremely high current and heat release, fire risk is greater than a decrease in resistance.
Safety hazards (especially in high voltage or high power situations):
Electric shock risk: Resistance failure (especially open circuit or increased resistance) in high-voltage circuits may cause dangerous high voltage to be carried by metal shells or touchable parts that should be grounded. Short circuit failure may also cause the low-voltage part to accidentally carry high voltage.
Arc/explosion: When a high-voltage resistor fails due to an open circuit, arc discharge may occur at the breakpoint, causing further damage or even igniting the surrounding environment. Some types of resistors, such as wound resistors and certain ceramic packages, may physically burst and produce splashes when severely overloaded.
Smoke/Toxic Gases: When a resistor overheats and burns out, its materials (resistor film, ceramic substrate, epoxy coating, leads) may release harmful smoke and gases.
Summarize key points:
The failure mode determines the consequences: the effects of open circuit, short circuit, and resistance changes are completely different.
The circuit function determines the scope of influence: the failure consequences of resistors vary greatly in different positions such as power supply, signal, control, and protection.
The consequences vary in severity: from minor performance degradation (which may not be easily noticeable) to complete equipment paralysis, to serious safety accidents such as fire or electric shock.
Joint damage is common: the failure of a resistor often "affects" other components around it, or even the entire system.
Therefore, in circuit design and maintenance, it is crucial to choose resistors with appropriate ratings (power, voltage, accuracy), ensure good heat dissipation, avoid overstress (voltage, current, temperature), and use protective components (such as fuses, TVS tubes) to prevent resistor failure and mitigate its consequences. When troubleshooting circuit faults, resistance is one of the key components that needs to be checked.