1. Lecture 3 Assignment 1. In addition to reading through Chapter 1 and starting chapter 2 read one paper on the exposures that you get from a low frequency source and write up a one page summary. Also you should start looking for papers on a topic you want to follow up on. 2. Be prepared to talk about what you have read for about 5 minutes in class on Wednesday. 3. People we do not get to on Wednesday will be asked to talk on Friday. 1

2. Bioelectromagnetics ECEN 5341/4341 Lecture 3 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

3. 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

4. Natural EM Power Density at the Earths Surface 4

5. B Field for Underwater Cable 5 Normal load 400A shielded so no E field outside

6. High Voltage AC Lines 6 Standards in US limit Fields to 1 to 5kV/m

7. Magnetic fields from Power Lines as a Function of Distance 7

8. The Effects of Power Pole Configurations and Phasing on Magnetic Fields 8

9. 1 9

10. Some Typical Magnetic and Electric Field Strengths vs. Distance 10

11. Fourier Spectrum of A Current Wave Form 11

12. Typical Magnetic Field Exposure Levels At Home 12

13. 1 13

14. Variations with time of Day 14

15. Variations in Magnetic Field Exposures Over the Course of a Day 15

16. Some Current Wave Forms 16

17. The Fourier Spectra of 1.7 17

18. Magnetic Fields Around Appliances 18

19. 1 19

20. Wave Shapes Near Fluorescent Light 20

21. Common Exposures 21

22. Exposures on Electric Trains 22

23. Electric Field Scaling and Induced Currents 23

24. Induced Electric Fields 24

25. A More Complete Model 25

26. 1 26

27. Electric and Magnetic Induced Current Densities 27

28. Internally Generated Voltages 28

29. 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 29

30. Computer Display Fields 1 30

31. 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 31

32. TV and Base Stations 32

33. Exposure Levels 1. US average about 50µW/m 2 to 100µW/m 2 2. We have measure E =1 to 2 V/m in Boulder, peak power density < 10 mW/m 2 3. Peak Power from transmitter about50 KW 4. Radar Peak at Megawatts, over the horizon 33

34. Frequencies 34