MadSci Network: Engineering |
Electromagnetics is the knowlege and theory about electric and magnetic fields. When they are changing with time, electric and magnetic fields are always accompanying each other, therefore generally called electromagnetic fields, they can also be called electromagnetic wave or electromagnetic energy. Electromagnetics have strong effect on our everyday life since without it many important technologies are impossible. Its main applications include 1) electric power generator 2) electric motor 3) radio and TV broadcasting 4) satellite TV 5) GPS 6) cell phones and mobile phones 7) wireless LAN 8) cable TV 9) microwave oven Electric power generator converts motion energy to electromangetic energy and electric moter converts it back. Microwave oven converts electromagnetic energy with low frequency to electromagnetic energy with very high frequency (several GHz), which is relatively easy to be absorbed by food and converted to heat. All other applications use electromagnetic wave to transfer information. To do so you need an oscillator to generate high frequency electromagnetic wave, then use a modulator to put the information on the electromagnetic wave, and use an antenna to send out the electromagnetic wave. The receiver then use an antenna to collect the electromagnetic energy which carries your information from air. Because the power is weak, generally he needs an amplifier to make it stronger, then use a demodulator to pick up the information from the high frequency electromagnetic energy. This is the case for radio, TV, satellite TV, GPS, cell phones and wireless LAN. Cable TV does not need antennas, instead, it transmit the electromagnetic wave through cables, like tap water running through tubes.
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