Among standard dielectric types (air, paper, mica, plastic film), which capacitor can store the highest amount of energy for a given volume and safe operating field?

Introduction / Context:
Capacitor energy storage depends on both the dielectric constant and the maximum electric field (dielectric strength) that the material can withstand without breakdown. Choosing the correct dielectric is essential in power electronics, pulse circuits, and precision timing applications.

Given Data / Assumptions:

• Comparison is among conventional, non-electrolytic dielectrics: air, paper, mica, plastic films.
• Energy density u = 1/2 * epsilon_0 * epsilon_r * E_max^2.
• We compare typical engineering values of epsilon_r and breakdown strength.

Concept / Approach:
Air has epsilon_r ≈ 1 and relatively low breakdown strength; paper has moderate epsilon_r but lower strength than engineered solids; many plastic films have moderate epsilon_r (≈2–3) and good strength; high-quality mica exhibits relatively high epsilon_r (≈5–7) and very high dielectric strength with excellent thermal stability. As a result, mica capacitors can be designed to store more energy safely per unit volume than air or paper and are competitive with (and often superior to) many plastic films for high-voltage, high-stability applications.

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