3. Dielectrics, Polarization and Interface Phenomena

Introduction and context

Electromagnetic fields in matter differ fundamentally from fields in free space because the material responds to an applied electric field. In a dielectric, this response is primarily associated with displacement of bound charges, rotation of permanent molecular dipoles, and, at higher frequencies, resonant motion of charges. These microscopic processes determine macroscopic quantities such as polarization, permittivity, susceptibility, dielectric loss, and electric displacement.

The subject is central to capacitor design, insulation coordination, microwave engineering, semiconductor devices, optical systems, energy storage, composites, and electromagnetic compatibility. It also provides the physical basis for electric-field boundary conditions at interfaces. A correct interface model must distinguish free charge from bound charge and must recognize that material properties may be scalar, tensorial, frequency-dependent, temperature-dependent, or field-dependent.

This chapter develops the field description of dielectrics from microscopic polarization to macroscopic constitutive laws. It then examines anisotropy, dispersion, loss, nonlinear behavior, composite media, and interfaces, with emphasis on interpretation and engineering application.

Learning objectives

After studying this chapter, the reader should be able to:

1. Explain polarization mechanisms and distinguish free, bound, and induced charge.

2. Relate polarization, susceptibility, permittivity, and electric displacement.

3. Derive bound volume and surface charge densities.

4. Apply electrostatic boundary conditions at dielectric interfaces.

5. Analyze dielectric loss, complex permittivity, dispersion, and relaxation.

6. Describe anisotropic and nonlinear dielectric behavior using constitutive models.

7. Evaluate dielectric interfaces and composites in practical field problems.

8. Recognize design limitations, measurement issues, and emerging material trends.

From molecular response to macroscopic polarization

A dielectric is an electrically insulating material in which charges are not free to conduct over macroscopic distances under ordinary operating conditions. Insulation does not mean that charges are immobile. An applied electric field slightly separates positive and negative charge centers within atoms or molecules. The resulting electric dipole moment is the vector product of charge and separation. If the dipole moment of one molecule is \(\mathbf p\), the polarization is defined as the dipole moment per unit volume:

\[

\mathbf P=\lim_{\Delta V\to 0}\frac{\sum_i\mathbf p_i}{\Delta V}.

\]

Its SI unit is coulombs per square metre. Polarization is a macroscopic field, although its origin is microscopic.

Four mechanisms are especially important. Electronic polarization results from displacement of the electron cloud relative to the nucleus and occurs extremely rapidly. Ionic polarization occurs in crystals containing positive and negative ions that shift relative to one another. Orientational, or dipolar, polarization arises when permanent molecular dipoles tend to align with the applied field; it is strongly affected by temperature and molecular mobility. Interfacial or space-charge polarization occurs when mobile or partially mobile charges accumulate at material boundaries, pores, defects, or electrode interfaces.

These mechanisms do not respond equally at all frequencies. Electronic polarization can follow optical-frequency fields, whereas orientational and interfacial mechanisms generally fail to follow sufficiently rapid field reversal. Consequently, permittivity is often frequency-dependent.

Polarization and induced charge

Polarization produces bound charge. For a polarized volume, the bound volume charge density is

\[

\rho_b=-\nabla\cdot\mathbf P,

\]

and the bound surface charge density at a boundary with outward unit normal \(\hat{\mathbf n}\) is

\[

\sigma_b=\mathbf P\cdot\hat{\mathbf n}.

\]

A uniform polarization inside an ideal homogeneous dielectric gives \(\rho_b=0\), but it can still produce surface charge at the boundary. Nonuniform polarization, by contrast, produces volume bound charge. These relations are essential in interpreting field distributions: polarization is not itself a charge density, but its divergence and normal component generate equivalent bound charges.

The total charge density may be written as

\[

\rho=\rho_f+\rho_b,

\]

where \(\rho_f\) is free charge supplied by electrodes, ionization, conduction, or external sources. The distinction is a modeling distinction rather than a claim that bound charge is physically unreal. It allows Maxwell’s equations to be written conveniently for matter.

Constitutive description of a dielectric

Gauss’s law in microscopic form is \(\nabla\cdot\mathbf E=\rho/\varepsilon_0\). Substituting the charge decomposition and using \(\rho_b=-\nabla\cdot\mathbf P\) gives

\[

\nabla\cdot(\varepsilon_0\mathbf E+\mathbf P)=\rho_f.

\]

This motivates the definition of electric displacement:

\[

\mathbf D=\varepsilon_0\mathbf E+\mathbf P,

\qquad \nabla\cdot\mathbf D=\rho_f.

\]

The displacement field is not generally equal to the electric flux density in a microscopic sense; it is a macroscopic auxiliary field whose divergence accounts for free charge.

For a linear, homogeneous, isotropic dielectric,

\[

\mathbf P=\varepsilon_0\chi_e\mathbf E,

\]

where \(\chi_e\) is electric susceptibility. Therefore,

\[

\mathbf D=\varepsilon_0(1+\chi_e)\mathbf E=\varepsilon\mathbf E,

\]

where \(\varepsilon\) is absolute permittivity and

\[

\varepsilon_r=\frac{\varepsilon}{\varepsilon_0}=1+\chi_e.

\]

Relative permittivity is dimensionless. In a linear medium, it describes how much electric displacement is produced by a given field compared with vacuum. It also affects capacitance, stored energy, wave velocity, reflection, and field concentration.

For a linear dielectric, the electrostatic energy density is

\[

w_e=\frac{1}{2}\mathbf E\cdot\mathbf D=\frac{1}{2}\varepsilon E^2.

\]

This expression assumes a reversible, nondispersive response. In dispersive or nonlinear media, stored and dissipated energy require more careful treatment.

Local-field interpretation

The macroscopic field is not identical to the microscopic field acting on an individual molecule. A common approximate model uses the Lorentz local field,

\[

\mathbf E_{\text{loc}}=\mathbf E+\frac{\mathbf P}{3\varepsilon_0},

\]

for a molecule in a spherical cavity within an isotropic polarized medium. If molecular polarizability is \(\alpha\), then \(\mathbf p=\alpha\mathbf E_{\text{loc}}\). Combining this with \(\mathbf P=N\mathbf p\) leads to the Clausius–Mossotti relation,

\[

\frac{\varepsilon_r-1}{\varepsilon_r+2}=\frac{N\alpha}{3\varepsilon_0}.

\]

The relation is an idealized bridge between molecular polarizability and bulk permittivity. It is less reliable for strongly interacting, ionic, polar, or highly nonuniform materials, but it clarifies why density and molecular structure influence dielectric behavior.

Interfaces and boundary conditions

Consider an interface between media 1 and 2 with unit normal directed from medium 1 to medium 2. In electrostatics, \(\nabla\times\mathbf E=0\), so integration around a narrow rectangular loop gives continuity of tangential electric field:

\[

\hat{\mathbf n}\times(\mathbf E_2-\mathbf E_1)=0.

\]

Thus, \(\mathbf E_{1t}=\mathbf E_{2t}\). Gauss’s law for displacement gives

\[

\hat{\mathbf n}\cdot(\mathbf D_2-\mathbf D_1)=\sigma_f,

\]

where \(\sigma_f\) is free surface charge at the interface. If no free surface charge exists, the normal component of \(\mathbf D\) is continuous.

The corresponding normal electric-field relation for isotropic media is

\[

\varepsilon_2E_{2n}-\varepsilon_1E_{1n}=\sigma_f.

\]

Even when \(\sigma_f=0\), normal electric field generally changes across an interface because \(E_n=D_n/\varepsilon\). A field entering a higher-permittivity medium becomes smaller in its normal component. Tangential field remains continuous in the electrostatic case, so the field vector usually changes direction. With no free surface charge, the field satisfies

\[

\frac{E_{1t}}{E_{2t}}=1,

\qquad

\frac{E_{1n}}{E_{2n}}=\frac{\varepsilon_2}{\varepsilon_1}.

\]

At an interface, polarization may create bound surface charge even when free surface charge is absent. The bound surface density is determined by the difference in polarization normal components:

\[

\sigma_b=(\mathbf P_1-\mathbf P_2)\cdot\hat{\mathbf n},

\]

with signs dependent on the chosen normal convention. Interface polarization is responsible for field discontinuities and is particularly important in layered insulation, semiconductors, biological materials, and composites.

For time-varying fields, the tangential electric-field condition remains continuous in the absence of an idealized magnetic surface flux impulse, while magnetic boundary conditions involve surface current. In practical low-frequency dielectric interfaces, the electrostatic relations are often adequate, but at microwave and optical frequencies the full electromagnetic boundary problem must be solved.

Anisotropic and nonlinear dielectrics

In an isotropic material, polarization is parallel to the electric field. In an anisotropic crystal this is not generally true. The constitutive law becomes

\[

\mathbf D=\boldsymbol{\varepsilon}\mathbf E,

\]

where \(\boldsymbol{\varepsilon}\) is a second-order permittivity tensor. In principal axes it may be diagonal:

\[

\begin{bmatrix}D_x\\D_y\\D_z\end{bmatrix}=

\begin{bmatrix}\varepsilon_x&0&0\\0&\varepsilon_y&0\\0&0&\varepsilon_z\end{bmatrix}

\begin{bmatrix}E_x\\E_y\\E_z\end{bmatrix}.

\]

The principal permittivities need not be equal. Uniaxial crystals have two independent values, while biaxial crystals have three. The orientation of the material axes relative to the field is therefore a design variable in electro-optic, piezoelectric, microwave, and antenna applications.

Nonlinear dielectric behavior occurs when polarization is not proportional to field. A simplified expansion is

\[

P=\varepsilon_0(\chi^{(1)}E+\chi^{(2)}E^2+\chi^{(3)}E^3+\cdots).

\]

In centrosymmetric bulk materials, the even-order terms often vanish under the ideal symmetry assumptions, although surfaces and engineered structures can break that symmetry. Nonlinear response enables frequency doubling, electro-optic modulation, parametric interaction, tunable capacitors, and ferroelectric switching. At strong fields, permittivity may depend on field amplitude, and hysteresis may cause substantial energy dissipation.

Ferroelectrics possess spontaneous polarization that can be reversed by an applied field. Their constitutive behavior is history-dependent, so a single-valued linear permittivity is insufficient. Device design must consider coercive field, remanent polarization, cycling, temperature, and fatigue.

Dispersion and dielectric loss

A real dielectric exhibits both storage and dissipation. For sinusoidal steady-state fields using the \(e^{j\omega t}\) convention, complex permittivity is commonly written

\[

\varepsilon^*(\omega)=\varepsilon'(\omega)-j\varepsilon''(\omega).

\]

The real part represents field-energy storage and the imaginary part represents dielectric loss under this convention. The loss tangent is

\[

\tan\delta=\frac{\varepsilon''}{\varepsilon'}.

\]

A dielectric with finite conductivity has an additional loss contribution. Since \(\mathbf J=\sigma\mathbf E\), conductivity can be represented by an effective complex permittivity term proportional to \(\sigma/\omega\). Thus low-frequency measurements may show large apparent loss even when the intrinsic polarization loss is modest.

Dispersion means that permittivity changes with frequency. A simple Debye relaxation model is

\[

\varepsilon^*(\omega)=\varepsilon_\infty+\frac{\varepsilon_s-\varepsilon_\infty}{1+j\omega\tau},

\]

where \(\varepsilon_s\) is the low-frequency permittivity, \(\varepsilon_\infty\) is the high-frequency limit, and \(\tau\) is the relaxation time. Maximum relaxation loss occurs near \(\omega\tau\approx1\). Real materials often require multiple relaxation times or Cole–Cole-type empirical models because of molecular distributions, interfaces, and defects.

Causality imposes a relationship between the real and imaginary parts of response; they cannot be chosen independently over all frequencies. This is expressed mathematically by Kramers–Kronig relations. The practical implication is that a sharp change in stored response is normally accompanied by a corresponding loss or phase effect over some frequency range.

Composite dielectrics and interface polarization

A composite combines two or more phases with different permittivities, conductivities, geometries, or relaxation times. Effective permittivity depends not only on the constituent values but also on volume fraction, connectivity, particle shape, orientation, dispersion quality, and interfacial bonding.

For ideal layers normal to the electric field, the electric displacement is approximately uniform in the absence of free charge at internal interfaces, leading to a series-type effective permittivity. For layers parallel to the field, the electric field is approximately common and a parallel-type average applies. These bounds are useful first estimates but do not describe arbitrary microstructures.

Maxwell–Garnett models are often used for dilute inclusions in a host, while Bruggeman-type models treat phases more symmetrically. Near a percolation threshold, a small change in filler concentration can cause a large change in effective conductivity and permittivity. Nanocomposites may exhibit strong interfacial polarization, commonly called Maxwell–Wagner polarization, because charges accumulate at boundaries between phases with different electrical properties.

Composite design involves trade-offs. High-permittivity fillers can increase capacitance but may raise loss, reduce breakdown strength, increase viscosity during processing, or create local field enhancement. Voids are especially dangerous in high-voltage insulation because their low permittivity changes field distribution and may initiate partial discharge.

Practical applications and professional decisions

In a capacitor, the capacitance of a uniform parallel-plate structure is approximately

\[

C=\frac{\varepsilon A}{d}.

\]

Replacing air with a dielectric increases capacitance, but the usable voltage is limited by dielectric strength, thermal behavior, loss, and aging. The designer must therefore optimize energy density rather than maximize relative permittivity alone.

In cable and transformer insulation, field grading is used to control stress concentration near electrodes, joints, and geometric discontinuities. Permittivity gradients, semiconductive screens, stress cones, and carefully controlled interfaces reduce local electric-field maxima. In printed circuit boards and high-speed interconnects, frequency-dependent permittivity and loss determine propagation delay, impedance, attenuation, and signal integrity.

Microwave resonators use dielectric materials for miniaturization and frequency control. The relevant material data include complex permittivity, temperature coefficient, anisotropy, and manufacturing variation. In optical systems, the frequency dependence of permittivity is related to refractive index through approximately \(n\approx\sqrt{\varepsilon_r}\) in a nonmagnetic, low-loss region, although absorption and dispersion must be included near resonances.

Measurement should match the intended operating regime. Capacitance methods are useful at low frequencies, impedance analyzers cover broader ranges, resonant methods provide high sensitivity at microwave frequencies, and transmission-line or waveguide methods characterize materials under propagation conditions. Results depend on electrode polarization, sample thickness, temperature, moisture, calibration, and fixture geometry.

Illustrative case study: field grading in a layered insulation system

Background

Consider a two-layer insulation system between parallel electrodes. Layer 1 has thickness \(d_1\) and relative permittivity \(\varepsilon_{r1}\); layer 2 has thickness \(d_2\) and relative permittivity \(\varepsilon_{r2}\). The layers are arranged normal to a uniform applied voltage, and no free charge exists at their internal interface.

Situation and analysis

Because there is no free charge at the interface, the normal component of \(\mathbf D\) is the same in both layers. Hence,

\[

\varepsilon_1E_1=\varepsilon_2E_2.

\]

The voltage is

\[

V=E_1d_1+E_2d_2.

\]

Solving gives

\[

E_1=\frac{V}{d_1+(\varepsilon_1/\varepsilon_2)d_2},

\qquad

E_2=\frac{V}{(\varepsilon_2/\varepsilon_1)d_1+d_2}.

\]

The lower-permittivity layer experiences the larger electric field. If its dielectric strength is lower, failure begins there even when the average field across the complete insulation appears safe.

Engineering approach

An engineer may alter thicknesses, select compatible permittivities, introduce a graded interface, remove voids, or use a semiconductive stress-control layer. The design must also account for frequency, temperature, moisture, manufacturing tolerances, and transient overvoltage. A material selected only by its nominal relative permittivity may perform poorly if its loss or breakdown strength is unsuitable.

Outcome and learning points

The case demonstrates that interface conditions govern voltage division in series dielectrics. The displacement field is continuous, but the electric field is not. It also shows why multilayer insulation must be evaluated locally rather than by average field. In practice, interface quality and void control can be as important as bulk material properties.

Challenges, limitations, and common errors

Several errors recur in dielectric analysis. First, \(\mathbf D\) is sometimes treated as universally continuous; it is continuous in its normal component only when free surface charge is zero. Second, continuity of the entire electric field vector is incorrectly assumed across dielectric interfaces; only the tangential electrostatic component is continuous. Third, relative permittivity is treated as a constant even when frequency, temperature, moisture, and field amplitude produce strong variation.

Another difficulty is separating conduction loss from polarization loss. Electrode polarization can distort low-frequency measurements, while fixture parasitics can corrupt high-frequency data. Homogenized composite models may conceal local field enhancement, interfacial charge, and defects. Linear constitutive laws are also inappropriate near ferroelectric switching, dielectric breakdown, or strong-field nonlinear operation.

Breakdown is not predicted solely by permittivity. Defects, thermal runaway, partial discharge, mechanical stress, aging, radiation, and chemical degradation may dominate. Safety margins should therefore be based on validated material data and relevant standards rather than ideal equations alone.

Professional, ethical, and regulatory considerations

Dielectric systems are safety-critical in power equipment, medical devices, aerospace systems, and high-voltage laboratories. Engineers must document material data, test conditions, uncertainty, aging assumptions, and traceability. Insulation coordination should follow applicable national and international standards, including requirements for impulse testing, creepage and clearance, partial discharge, thermal endurance, and environmental qualification.

Ethical practice requires that measured loss, breakdown results, and failure rates not be selectively reported. A material tested under dry laboratory conditions must not be represented as suitable for humid, contaminated, or high-temperature service without evidence. Design reviews should consider foreseeable misuse, fire behavior, environmental impact, recyclability, and end-of-life handling of advanced composites and electronic materials.

Technology and emerging directions

Modern electromagnetic simulation packages represent anisotropic, dispersive, and nonlinear materials through tensor constitutive laws, fitted relaxation models, lookup tables, or field-dependent functions. Accurate broadband simulation requires causal material models; an arbitrary fitted permittivity curve can produce nonphysical time-domain behavior.

Current research includes high-energy-density polymer nanocomposites, self-healing insulation, tunable ferroelectrics, metamaterials, low-loss microwave ceramics, bio-based dielectrics, and materials engineered for simultaneous high permittivity and high breakdown strength. Machine learning is increasingly used to screen formulations and infer material parameters from impedance or spectroscopy data. Such tools support, but do not replace, physical validation, uncertainty analysis, and explainable engineering judgment.

Best practices for dielectric analysis

A sound analysis begins by specifying frequency, temperature, field amplitude, geometry, and environmental conditions. The analyst should then choose the appropriate constitutive model: scalar, tensorial, complex, nonlinear, or composite. Boundary conditions must be applied to free charge and field components with consistent normal directions. Material data should be measured or sourced under conditions matching operation, and local field maxima should be examined rather than relying only on average values.

For design work, dielectric strength, loss tangent, thermal conductivity, aging, manufacturability, and interface quality should be evaluated together. Numerical results should be checked against limiting cases, conservation laws, dimensional consistency, and independent measurements.

Chapter Summary

Dielectric behavior originates in the response of bound charges to an electric field. Polarization is dipole moment per unit volume, and its divergence and boundary-normal component generate bound volume and surface charges. The displacement field \(\mathbf D=\varepsilon_0\mathbf E+\mathbf P\) separates the effect of free charge from material polarization. In a linear isotropic medium, susceptibility and relative permittivity are related by \(\varepsilon_r=1+\chi_e\).

At interfaces, tangential electric field is continuous in electrostatics, while the normal displacement changes according to free surface charge. Consequently, electric field normally changes across a dielectric boundary. Real materials may be anisotropic, nonlinear, lossy, dispersive, or composite. Complex permittivity describes storage and loss, while relaxation models describe frequency-dependent response. Composite interfaces can produce strong Maxwell–Wagner polarization and local field enhancement. Sound engineering design therefore requires simultaneous attention to constitutive properties, interfaces, breakdown, measurement conditions, aging, safety, and model validity.

Key Terms

Polarization: Electric dipole moment per unit volume in a material.

Bound charge: Charge associated with polarization rather than freely supplied conduction or electrode charge.

Free charge: Charge treated as an external or mobile source in the macroscopic field model.

Electric displacement: Macroscopic field defined by \(\mathbf D=\varepsilon_0\mathbf E+\mathbf P\).

Electric susceptibility: Dimensionless proportionality between polarization and electric field in a linear dielectric.

Permittivity: Material property relating electric displacement to electric field under a specified constitutive model.

Relative permittivity: Ratio of material permittivity to vacuum permittivity.

Electronic polarization: Polarization caused by displacement of electron clouds relative to nuclei.

Orientational polarization: Alignment of permanent molecular dipoles with an applied field.

Interfacial polarization: Charge accumulation at boundaries between regions with different electrical properties.

Anisotropy: Dependence of material response on direction.

Nonlinear dielectric: Material whose polarization is not proportional to electric field.

Complex permittivity: Frequency-domain quantity whose real and imaginary parts represent storage and loss.

Loss tangent: Ratio \(\varepsilon''/\varepsilon'\), indicating dielectric loss relative to storage.

Dispersion: Dependence of a constitutive property on frequency.

Relaxation time: Characteristic time over which a polarization mechanism responds to a changing field.

Maxwell–Wagner polarization: Interfacial charge accumulation in heterogeneous or composite materials.

Dielectric strength: Maximum electric-field stress a material can withstand before breakdown under specified conditions.

Review Questions

Short Answer Questions

1. Define polarization and state its SI unit.

2. Distinguish free charge from bound charge.

3. State the relation between susceptibility and relative permittivity for a linear isotropic dielectric.

4. What is meant by dielectric loss tangent?

5. Why can the normal electric field change across a charge-free dielectric interface?

Long Answer Questions

1. Derive the expressions for bound volume and bound surface charge densities and explain their physical meaning.

2. Derive the electrostatic boundary conditions for \(\mathbf E\) and \(\mathbf D\) at an interface.

3. Explain electronic, ionic, orientational, and interfacial polarization mechanisms and their frequency dependence.

4. Discuss complex permittivity, Debye relaxation, dielectric loss, and the effect of conductivity on measured response.

5. Explain anisotropic and nonlinear dielectric constitutive models and identify applications in which they are important.

Analytical / Application Questions

1. Two charge-free dielectric layers are connected in series between parallel electrodes. Derive the electric field in each layer and determine which layer experiences the greater field.

2. A composite insulation contains high-permittivity particles in a low-permittivity polymer. Analyze how particle concentration, interface polarization, voids, and particle shape may affect effective permittivity and breakdown reliability.

3. A microwave material shows a strong change in measured permittivity and loss near a particular frequency. Propose a physical interpretation, an appropriate constitutive model, and a measurement strategy for validating the interpretation.

22. Multiple Choice Questions with Answers

Question 1

For a linear isotropic dielectric, which relation is correct?

A. εr = χe − 1

B. εr = 1 + χe

C. χe = ε0εr

D. D = E/ε

Correct Answer: B. εr = 1 + χe

Question 2

A uniformly polarized dielectric has no volume bound charge in its interior when

A. P is parallel to the interface

B. P is time-varying

C. ∇·P = 0

D. P is perpendicular to the interface

Correct Answer: C. ∇·P = 0

Question 3

At an electrostatic interface with no free surface charge, which quantity has continuous normal component?

A. E

B. P only

C. D

D. εr

Correct Answer: C. D

Question 4

Two dielectric layers are arranged in series with no free charge at their interface. Which statement is correct?

A. The electric fields are equal in both layers

B. The normal displacement fields are equal

C. The tangential displacement fields are equal

D. The voltage drops are always equal

Correct Answer: B. The normal displacement fields are equal

Question 5

For the convention ε* = ε' − jε'', the loss tangent is

A. ε'/ε''

B. ε''/ε'

C. ε'ε''

D. ε'' − ε'

Correct Answer: B. ε''/ε'

Question 6

In a Debye dielectric, the strongest relaxation loss generally occurs when

A. ωτ is approximately 1

B. ωτ is zero for all materials

C. ωτ is infinitely large

D. τ is independent of frequency and field

Correct Answer: A. ωτ is approximately 1

Question 7

In an anisotropic dielectric, the relation between D and E is generally represented by

A. A scalar conductivity only

B. A permittivity tensor

C. A universal vacuum constant

D. A magnetic permeability tensor only

Correct Answer: B. A permittivity tensor

Question 8

A low-permittivity layer placed in series with a high-permittivity layer generally experiences

A. The smaller normal electric field

B. The larger normal electric field

C. Zero displacement field

D. No polarization charge

Correct Answer: B. The larger normal electric field

Question 9

Maxwell–Wagner polarization is primarily associated with

A. Charge accumulation at interfaces in heterogeneous materials

B. Electron motion in vacuum

C. Magnetic hysteresis in ferromagnets

D. Uniform polarization with no material boundaries

Correct Answer: A. Charge accumulation at interfaces in heterogeneous materials

Question 10

Why can a high-permittivity filler reduce the reliability of a composite dielectric?

A. It always eliminates polarization

B. It can increase local field enhancement, loss, or processing defects

C. It forces the electric field to vanish everywhere

D. It makes dielectric strength independent of microstructure

Correct Answer: B. It can increase local field enhancement, loss, or processing defects