Can the Poynting Vector Be Applied to DC Current?

AI Thread Summary
The discussion explores the applicability of the Poynting vector to DC current, questioning whether the theorem used for AC systems can also be valid for DC. It highlights that when electricity was first introduced, it generated a transient response with a wide frequency spectrum. The example of turning a DC LED light on and off illustrates that DC can be seen as a low-frequency AC signal due to its periodic nature. Participants argue that the fundamental principles of energy transfer via the Poynting vector should apply to both AC and DC systems. Ultimately, the conversation emphasizes the interconnectedness of AC and DC in terms of energy transfer analysis.
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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