Radiowave Transmission: Where Does Electric Field Come From?

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SUMMARY

The electric field in an electromagnetic (EM) wave emitted by an antenna originates from the alternating current (AC) voltage source connected to the antenna. When charges accelerate due to the AC voltage, they create an electric field that propagates as part of the EM wave. Unlike a normal wire, where the electric field is neutralized by positive atomic charges, the antenna operates as an open circuit, allowing charges to flow out and back at the frequency of transmission. This mechanism is essential for understanding radiowave transmission and the generation of electric fields in antennas.

PREREQUISITES
  • Understanding of electromagnetic waves
  • Knowledge of alternating current (AC) voltage sources
  • Familiarity with antenna theory
  • Basic principles of electric fields and charge behavior
NEXT STEPS
  • Research the principles of electromagnetic wave propagation
  • Study antenna design and its impact on radiowave transmission
  • Explore the relationship between AC voltage and electric field generation
  • Learn about the behavior of charges in open versus closed circuits
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Electrical engineers, physicists, students studying electromagnetism, and anyone interested in the principles of radiowave transmission and antenna functionality.

Jimmy87
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Hi, I am having difficulty determining where the electric field comes from when an electromagnetic wave is emitted by an antenna. I know that the charges accelerate between an AC voltage but where does the electric part of the EM wave come from? In a normal wire there is no electric field from the charges themselves as they are canceled by the positive charges of the atoms. The electric field in the wire comes from the source voltage (e.g. a battery). So in an antenna does the electric field come from the AC voltage source?
 
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Yes, the voltage source puts a charge on the antenna. Note that an antenna is not a closed circuit. Charges flow out of and back into each end at the same rate as the transmitted frequency.
 

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