Capacitor equivalent circuit – leakage resistance (parallel R) requirement A practical capacitor is often represented by an ideal capacitance in parallel with a resistance that models insulation/leakage. For a good-quality capacitor used in electronics and power systems, this parallel resistance should be:

Introduction / Context:
Real capacitors are not perfect: in addition to the ideal capacitance, they exhibit dielectric losses and leakage. Engineers often use an equivalent circuit with a capacitance in parallel with a resistance to represent the insulation resistance or leakage path through the dielectric. Understanding what value of this resistance indicates a 'good' capacitor is crucial for low-loss filtering, energy storage, timing, and hold-up applications.

Given Data / Assumptions:

• The capacitor is modeled as C in parallel with R_leak (insulation resistance).
• Applications may involve DC bias or AC ripple; long-term voltage holding is desired.
• We compare qualitative magnitudes: negligible, low, high, very high.

Concept / Approach:

The parallel resistance determines the DC leakage current and contributes to AC loss. A larger R_leak means less leakage and less power dissipated as heat. For a 'good' capacitor, we want negligible leakage and near-ideal energy storage, which corresponds to an R_leak that is as large as practically achievable (approaching open circuit). This also translates to a high parallel quality factor and a large time constant for charge retention.

Step-by-Step Solution:

Verification / Alternative check:

Datasheets specify insulation resistance (IR) or leakage current. High-grade film and ceramic capacitors show megaohm to gigaohm IR values, confirming that 'very high' leakage resistance is the desired characteristic.

Why Other Options Are Wrong:

'Negligible' or 'low' resistance would cause large leakage and high loss; 'high' is good but 'very high' best reflects the design goal; 'moderate' is inadequate for precision timing or energy storage.

Common Pitfalls:

Confusing the parallel leakage model with series ESR; ESR affects AC ripple but does not set DC leakage. Also, assuming all dielectric losses are captured by ESR alone ignores the parallel leakage path.

Final Answer:

very high