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Bioelectromagnetics ECEN 5031/4031 Lecture 3

Bioelectromagnetics ECEN 5031/4031 Lecture 3. ITP Fellowships , Programing Air Force Internships Human Center Research 01-15-14 1. Environmental and Occupationally Encountered Electromagnetic Fields

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Bioelectromagnetics ECEN 5031/4031 Lecture 3

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  1. Bioelectromagnetics ECEN 5031/4031 Lecture 3 • ITP Fellowships , Programing Air Force Internships Human Center Research 01-15-14 • 1. Environmental and Occupationally Encountered Electromagnetic Fields • 2. The objective is to get a feel for the size of both the natural fields we are exposed to and the size of the fields that we are now exposed to resulting from the wide spread use of electricity.

  2. Atmospheric Sources • 1. Direct Current and ELF (0 to 3khz) • 2. Earths DC Magnetic Fields 24μT to 65μT variation up to about 1μT with the Northern Lights over several minutes • 3. Electric fields DC 100 to 300V/m with the earth negative. Up to 100kV/m in thunderstorms.

  3. Natural EM Power Density at the Earths Surface

  4. B Field for Underwater Cable Normal load 400A shielded so no E field outside

  5. High Voltage AC Lines Standards in US limit Fields to 1 to 5kV/m

  6. Magnetic fields from Power Lines as a Function of Distance

  7. The Effects of Power Pole Configurations and Phasing on Magnetic Fields

  8. Fourier Spectrum of A Current Wave form

  9. Typical Magnetic Field Exposure LevelsAt Home

  10. Variations in Magnetic Field Exposures Over the Course of a Day

  11. Some Current Wave Forms

  12. The Fourier Spectra of 1.7

  13. Magnetic Fields Around Appliances

  14. Some Typical Magnetic and Electric Field Strengths vs. Distance

  15. Wave Shapes Near Fluorescent Light

  16. Common Exposures

  17. Exposures on Electric Trains

  18. Electric Field Scaling and Induced Currents

  19. Electric and Magnetic Induced Current Densities

  20. Internally Generated Voltages

  21. Sources of Intermediate and Radio Frequency Fields • 1. Scanners , Libraries, Airport Security • 920MHz , B = 10µT and Deactivate at 50-60Hz 500µT • 2. Video Display Terminals, VDT, Cathode Ray Tubes CRT Up to 20KV inside the Tube, ≈10V/m at 0.5m

  22. Computer Display Fields • 1

  23. RF Sources • 2. RF heaters for sealing plastic etc. • 3. RF Transmission Short Wave 2 -27MHz 3-20V/m at 10’s of meters. • 4. Radio TV • 5. Base Stations and Cell Phones

  24. TV and Base Stations

  25. Exposure Levels • 1. US average about 50µW/m2 to 100µW/m2 • 2. We have measure E =1 to 2 V/m in Boulder, peak 10mw • 3. Peak Power from transmitter about50 KW • 4. Radar Peak at Megawatts, over the horizon

  26. Frequencies

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