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Dispersion and Absorption in Dielectrics I. Alternating Current Characteristics

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Kenneth S. Cole, Robert H. Cole · 1941

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This foundational 1941 research established principles still used today to calculate electromagnetic energy absorption in biological tissues.

Plain English Summary

Summary written for general audiences

This 1941 technical study by K.S. Cole examined how dielectric materials (insulators like those in electronic devices) respond to alternating current electrical fields. The research explored fundamental properties like dielectric constants and relaxation times that determine how materials absorb and scatter electromagnetic energy.

Why This Matters

While this may seem like ancient technical research, Cole's work laid critical groundwork for understanding how electromagnetic fields interact with biological tissues. The dielectric properties he studied in 1941 are the same principles that determine how your body absorbs energy from cell phones, WiFi routers, and other wireless devices today. Every calculation of specific absorption rate (SAR) - the measure of how much RF energy your tissue absorbs - relies on dielectric constants and relaxation times like those Cole investigated.

What makes this particularly relevant is that biological tissues are essentially complex dielectric materials with water content, proteins, and cellular structures that respond to electromagnetic fields in predictable ways. Understanding these fundamental interactions helps explain why certain frequencies penetrate deeper into tissue and why pulsed signals may have different biological effects than continuous waves.

Figures from the Original Paper

Diagrams extracted from the original research document.

chartPage 2 - Fig. 1: Real and imaginary parts of the dielectric constant plotted against frequency.
p. 2 of the original PDF
diagramPage 3 - AI-described figure: Fig. 2: Theoretical complex plane loci of the complex dielectric constant and equivalent circuits for dielectrics; (a) Debye theory, (b) as required by experimental evidence.
p. 3 of the original PDF
chartPage 4 - Fig. 4: Complex dielectric constants of liquids
p. 4 of the original PDF
chartPage 5 - Fig. 6: Complex dielectric constants of organic crystalline solids.
p. 5 of the original PDF
chartPage 6 - Figure 8. Frequency dependence of the complex dielectric constants of ice and glycerine, as explained in the text.
p. 6 of the original PDF
graphPage 10 - Figure 9. Distribution of relaxation times F(s), where s = logₐ(τ/τ₀): (a) calculated from circular arc locus for α=0.23, (b) logarithmic Gaussian distribution for b=0.6.
p. 10 of the original PDF

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 1 GHz to 1 THz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 1 GHz to 1 THzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study.

Study Details

To present the results of an analysis of representative experimental data on dispersion and absorption in dielectrics, particularly focusing on the deviation from the Debye theory and the validity of the circular arc locus representation.

The study analyzed dispersion and absorption data from various liquids and solids, including water, ...

Experimental data for various dielectrics (liquids and solids) were found to be inconsistent with th...

The circular arc locus and the equivalent analytic representation of Eq. (5) provide an excellent description of dispersion in a large number of dielectrics. This description requires the introduction of a single parameter 'a' in addition to the constants €0, €x, and 70. The results suggest that the dispersion mechanism involves energy storage in addition to dissipation, with a phase angle independent of frequency. The simple mechanisms proposed to explain dielectric absorption (viscous damping, direct current conductivity) are purely dissipative and cannot account for the observed complex impedance behavior.

Cite This Study
Kenneth S. Cole, Robert H. Cole (1941). Dispersion and Absorption in Dielectrics I. Alternating Current Characteristics.
Show BibTeX
@article{dispersion_and_absorption_in_dielectrics_i_alternating_current_characteristics_g6591,
  author = {Kenneth S. Cole and Robert H. Cole},
  title = {Dispersion and Absorption in Dielectrics I. Alternating Current Characteristics},
  year = {1941},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

Dielectric properties describe how materials respond to electromagnetic fields - specifically how they store and dissipate electrical energy. These properties determine how deeply EMF penetrates into materials like biological tissue and how much energy gets absorbed.
Dielectric constants determine how electromagnetic energy travels through and gets absorbed by tissue. Higher dielectric constants typically mean greater energy absorption, which is why water-rich tissues like brain and muscle absorb more EMF than bone or fat.
Relaxation time describes how quickly a material's electrical properties respond to changing electromagnetic fields. Different relaxation times help explain why certain frequencies interact differently with biological tissues and why pulsed signals may have unique effects.
Cole's 1941 work established fundamental principles still used today to calculate specific absorption rates (SAR) and predict how electromagnetic fields interact with biological tissues. This foundational research underlies modern EMF safety standards and exposure assessments.
Wireless devices use alternating electromagnetic fields at specific frequencies. Understanding how these alternating currents interact with dielectric materials helps predict energy absorption patterns in biological tissues and explains frequency-dependent biological effects.