Diagnosing capacitor faults When a capacitor is described as “leaky,” what has happened to its dielectric property compared to normal?

Introduction / Context:
Capacitor health strongly affects power supplies, timing circuits, and filters. A common failure mode is leakage, where the dielectric no longer insulates effectively, allowing DC current to pass through and disturbing circuit operation.

Given Data / Assumptions:

• Capacitor previously functioning as a near-open to DC (very high insulation resistance).
• Observed symptom: unwanted DC current, self-heating, or inability to hold charge.
• Focus is on dielectric behavior rather than lead or mechanical faults.

Concept / Approach:
An ideal capacitor blocks DC because the dielectric has extremely high resistance. If the dielectric degrades, its effective resistance drops, creating a leakage path. This increases standby losses, can shift bias points, and may cause thermal runaway in severe cases.

Step-by-Step Solution:
Healthy state: very large insulation resistance → negligible DC current.Leaky state: insulation resistance decreases significantly.Effect: measurable DC current flows through the capacitor, discharging it and altering circuit operation.Conclusion: leakage corresponds to decreased dielectric resistance.

Verification / Alternative check:
Measure capacitor leakage with a megohmmeter or apply rated DC and observe current; compare against datasheet leakage specifications to confirm degradation.

Why Other Options Are Wrong:
It is open: that would show infinite resistance and zero capacitance effect, not leakage.It is shorted: an extreme failure; leakage is partial conduction, not a near-zero resistance short.Dielectric resistance increased: opposite of the observed leaky behavior.

Common Pitfalls:
Confusing ESR (equivalent series resistance) rise with insulation resistance drop; both are different parameters.Overlooking temperature dependence; leakage often increases as temperature rises.

Final Answer:
The dielectric resistance has decreased