Can the Poynting Vector Be Applied to DC Current?

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SUMMARY

The Poynting vector can indeed be applied to DC current, as it is fundamentally a tool for calculating energy transfer in both AC and DC systems. The discussion highlights that DC can be viewed as a very low frequency AC signal, particularly when considering the transient behaviors and pulse trains created by devices like LED lights. The application of Poynting's theorem to DC systems is supported by the understanding that energy transfer occurs in both scenarios, albeit with different frequency characteristics.

PREREQUISITES
  • Understanding of Poynting's theorem
  • Basic knowledge of AC and DC electrical systems
  • Familiarity with Fourier analysis
  • Concept of transient signals in electrical engineering
NEXT STEPS
  • Research the mathematical formulation of Poynting's theorem
  • Study the characteristics of transient signals in DC circuits
  • Explore the relationship between AC and DC signals through Fourier analysis
  • Investigate practical applications of Poynting vector in electrical engineering
USEFUL FOR

Electrical engineers, physicists, and students studying electromagnetism who are interested in the application of Poynting's theorem to both AC and DC systems.

Jackson Lee
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We all know that poynting vector could be used to calculate energy transferred in AC system, but I want to know if that theorem could also be applied to DC current? How to prove this? And how to prove energy transferred in AC system could be calculated via poynting vector?
 
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Why should DC be any different to AC?

When electricity was invented and the first contacts closed, a transient step occurred that had a continuous Fourier spectrum, covering periods of a nanosecond out to many centuries.

When you turn a DC LED light on at dusk, then off when you go to bed, that is just a delta function on the scale of the year. If you do it every night of the year, it becomes a year long pulse train, which has an AC component with a real DC component.

DC is really just very low frequency AC.
 

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