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Electromagnetic fields and applications

Electromagnetic fields and applications. Dr. Jonathan Bredow. F ields and their applications. A field relates to the spatial distribution of some quantity of interest The field may be described by a scalar, or it may be described by a vector Pressure example (scalar field).

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Electromagnetic fields and applications

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  1. Electromagnetic fields and applications Dr. Jonathan Bredow

  2. Fields and their applications • A field relates to the spatial distribution of some quantity of interest • The field may be described by a scalar, or it may be described by a vector • Pressure example (scalar field) http://www.usairnet.com/weather/maps/current/barometric-pressure/

  3. Fields and their applications • Wind direction example http://www.ambientweather.com/cuunstwimap.html • Wind direction and barometric pressure are related by the • gradient operator

  4. Common fields in electrical engineering • An Electric Field is produced by charges, and influences other charges (single charge example) http://www.google.com/search?q=electric+field+lines&hl=en&prmd=imvnsfd&tbm=isch&tbo=u&source=univ&sa=X&ei=id5pT6vhIqapsQKStvmOCQ&sqi=2 &ved=0CCwQsAQ&biw=1027&bih=521

  5. Common fields in electrical engineering • A Magnetic Field is produced by charges in motion, and influences other charges in motion http://www.google.com/search?q=magnetic+field&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=jttpT665D-LQsgLX4dikCQ&ved= 0CF8QsAQ&biw=1027&bih=521

  6. Applications involving electric/magnetic fields • Influence position or motion of charges by producing fields (CRT, MRI) • Sense information about the surrounding electric/magnetic environment from the fields being produced (Power line monitoring, Hall-effect detectors), or from how fields are disturbed (Metal detection, MRI) • Energy storage (Capacitor – electric field, inductor – magnetic field) • Energy conversion – transformers, motors, relays • Many applications for waves involving electric and magnetic fields (more coming on this)

  7. Waves • Wave - a disturbance or variation that transfers energy progressively from point to point in a medium and that may take the form of an elastic deformation or of a variation of pressure, electric or magnetic intensity, electric potential, or temperature • http://www.acs.psu.edu/drussell/Demos/waves-intro/waves-intro.html • Time varying electric fields couple with (result in) time varying magnetic fields and vice-versa leading to a wave of energy referred to as an electromagnetic (EM) wave which propagates away from the source at the speed of light (in open air or vacuum). • For practical applications EM waves may propagate in free space, or they may be confined to structures referred to as transmission lines.

  8. Transmission lines • Circuit models http://www.google.com/search?q=transmission+lines&hl=en&prmd=imvnsb&tbm=isch&tbo=u&source=univ&sa=X&ei=zyNqT8i1IbHLsQKH_8WVCQ &ved=0CHgQsAQ&biw=1097&bih=535

  9. Practical transmission lines • Coaxial line • Twisted pair • Microstrip • Waveguide • Fiber optics • Optical lens systems (wave beam modes)

  10. Applications of transmission lines • Microwave circuits http://www.google.com/search?q=microwave+circuits&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=ByhqT7e-JoHctgeTibTkCA&sqi=2& ved=0CFUQsAQ&biw=1097&bih=535

  11. Applications of transmission lines (2) • Optical lens systems http://www.google.com/search?q=compound+lens&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=mClqT9bmLtLqtgfL1OWPCQ& sqi=2&ved=0CFAQsAQ&biw=1097&bih=535

  12. Applications of transmission lines (3) • Other – What do you think?

  13. Applications of free space EM waves – communications • Broadcast radio/television • Radio and television (Analog and HD) • Analog and Digital, AM, FM, SW & Satellite • Two-way radio communication • Point-to-point (Family radio, emergency communications) • Wire replacement (Bluetooth) • Networked (internet, 802.11) • Cellular (CDMA, GSM, 3G, 4G)

  14. Radar: determining range to objects t = 2R/c, where R is range to the object 1 msec corresponds to 150 m http://www.radartutorial.eu/01.basics/rb04.en.html

  15. Doppler Shift - Relationship between wavelength, l, and frequency, f, is c= fl - Distance traveled during one period of the waveform is x= v/f • The apparent wavelength is thus • l’=l – x, or l’ = (c-v)/f ‘ - Hence, the apparent frequency is f’ = c/l’ = f(1/(1-v/c)) - The Doppler shift is then fd=f’-f http://imagine.gsfc.nasa.gov/YBA/M31-velocity/Doppler-shift-2.html

  16. Radar applications • Weather monitoring • Speed monitoring • Aircraft monitoring • Surveillance • Remote sensing from space

  17. UTA anechoic chamber – purpose?

  18. Radiometry • All objects emit EM energy according to Planck’s Law • Radiometry applications • Assessing heat leakage (for example, in a home) • Assessing heating/overheating in devices and systems • Radioastronomy • Night vision

  19. Antennas • Antennas are designed to efficiently radiate or capture radio frequency energy – cellular basestation example http://www.google.com/search?q=antenna+images&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=7jJqT6WmJ OyGsALe6oyjCQ&ved=0CD4QsAQ&biw=1097&bih=535

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