The electromagnetic field

Chapter The electromagnetic field

Teach Yourself Electricity and Electronics Third Edition Book
Pages 748
Views 8,878
Downloads : 12 times
PDF Size : 4.4 MiB

Summary of Contents

Teach Yourself Electricity and Electronics Third Edition Book

  • from a distance, the dots are too small to be individually discernible. Various combinationsof red, blue, and green intensities result in reproduction of all possible hues and satura-tions of color.The electromagnetic fieldIn a radio or television transmitting antenna, electrons are moving back and forth at anextreme speed. Their velocity is constantly changing as they speed up in one direction,slow down, reverse direction, speed up again, and so on. Any change of velocity is ac-celeration.When electrons move, a magnetic field is created. When electrons accelerate, achanging magnetic field is produced. An alternating magnetic (M) field gives rise to analternating electric (E) field, and this generates another changing M field. The processhas come full circle. Thus it repeats, the effects propagating through space at the speedof light. The E and M fields expand alternately outward from the source in sphericalwavefronts. At any given point in space, the E flux is perpendicular to the M flux. Thedirection of wave travel is perpendicular to both the E and M flux lines (Fig. 26-14).The EM flux field can oscillate at any conceivable frequency, ranging from manyyears per cycle to quadrillions of cycles per second. The sun has a magnetic field that os-cillates with a 22-year cycle. Radio waves oscillate at thousands, millions, or billions of cy-cles per second. Infrared, visible light, ultraviolet, and X rays oscillate at many trillions ofcycles per second. All of these effects are electromagnetic fields, and as such, they all490 Data transmission26-13An FSTV signal. This shows one line of data.