Dielectric loss versus frequency In electrical insulation engineering, dielectric materials exhibit energy dissipation when stressed by an alternating electric field. Consider the statement: “The dielectric losses do not depend on frequency.” Determine whether this statement is true or false, and justify the correct understanding of how loss varies with frequency in real dielectrics used in capacitors, cables, and high-voltage equipment.

Introduction / Context:
Dielectric loss represents the conversion of electrical energy into heat when a dielectric is subjected to an alternating electric field. Understanding its frequency dependence is essential for selecting insulation in capacitors, power cables, transformers, and RF components because excess loss causes heating, efficiency reduction, and accelerated aging.

Given Data / Assumptions:

• Real (non-ideal) dielectrics have finite loss tangent tan δ.
• Applied field varies sinusoidally with angular frequency ω.
• Material parameters may vary with frequency due to polarization mechanisms.

Concept / Approach:

For a linear dielectric, average volumetric loss is often modeled as P_loss = ω * ε0 * ε′ * tan δ * E_rms^2, where ε′ is the real part of permittivity and tan δ = ε′′/ε′ is the loss tangent. Multiple polarization processes (electronic, ionic, dipolar, interfacial) have characteristic relaxation times, so ε′ and ε′′ both depend on frequency. Hence dielectric loss typically varies strongly with frequency, often exhibiting peaks near relaxation frequencies.

Step-by-Step Solution:

Verification / Alternative check:

Datasheets of common dielectrics (e.g., XLPE, mica, PTFE, ceramics) publish tan δ versus frequency curves. Laboratory impedance spectroscopy directly shows ε′′(ω) and tan δ(ω) varying with ω, confirming frequency dependence.

Why Other Options Are Wrong:

Option A contradicts established models; C is incorrect because even at 50/60 Hz, materials show distinct tan δ; D is a tautology about an idealized lossless dielectric, not engineering reality; E arbitrarily restricts the frequency range and is not generally valid.

Common Pitfalls:

Assuming a constant tan δ across wide frequency ranges; ignoring temperature’s coupled effect on dielectric relaxation; confusing series ESR with dielectric loss mechanisms.

Final Answer:

False