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What exactly is electrical energy?

  1. Aug 17, 2009 #1
    My specific question is "How is electrical energy made available to devices?"

    Everyone knows that "devices transfer electrical energy into useful forms" of energy, such as light and heat. What I have discovered is that no source I have found has been able to describe exactly how devices GET that electrical energy.

    I understand potential differences, voltages, current, power, and almost anything else about electrical circuits, but what I cannot find, even in my "Physics for Scientists and Engineers" nor any of my Freshman Engineering texts is how these devices get energy.

    So my question stands, slightly modified, as:

    "How does an electrical current enable the transfer of electrical energy to devices?"

    Thank you.
  2. jcsd
  3. Aug 17, 2009 #2


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    Staff: Mentor

    The energy originally comes in chemical, mechanical, solar, and other sources, and is transferred to the devices via the electric grid:


    Welcome to the PF, BTW.
  4. Aug 17, 2009 #3
    I'm sorry, I didn't phrase my question appropriately. I know exactly how devices are connected and how energy sources are transferred into electrical energy. I'm looking for information on how exactly a device is delivered this electric energy through a current.

    For example, if I have a simple circuit like 2 batteries, a resistor, and an led, circuit analysis will tell me how many watts each device is consuming (assuming a perfectly conducting wire) and what the "voltage drops" across each element is, as well as the current, but I'm interested in how these elements are using said power. Undoubtedly this answer is extremely complex, but I'm not satisfied with the simple explanations I've been given.

    EDIT: If the flow of only electrons creates a current and a stable electrical circuit, and so does the flow of only protons, that would mean that ANY electrical current can transfer energy, and that the energy is transferred by the current, right? And if that's true, then does the direction that the energy is travelling play a bigger role than we've ever been taught (ie: conventional current is the direction that positive charges would move)?
    Last edited: Aug 17, 2009
  5. Aug 17, 2009 #4


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    Staff: Mentor

    The current through the resistor causes heat (in the classical model) because of the electrons transferring their momentum to the atomic lattice by collisions. The concept of "phonons" comes into play in this model. You can use wikipedia or google or Wolfram ! Alpha to learn more about electron-lattice collisions and phonons.

    I haven't studied LEDs for a long time, so you'd need to use the search engines I mentioned to read more about the mechanism that results in the excited electrons transitioning to lower enegy orbitals and giving off photons in those transitions. Jeeze, I need to read up on that sometime...

    Similarly, for each consumer of electrical power, just read about the device to see how the conversion takes place. If you're confused about a particular consumer mechanism, you can post that specific question here, and you should get a pretty good answer.

    Not sure of the question, sorry. First, it is the electrons in the conduction band of metals that carry current, not protons. Protons are held captive by the atomic lattice; electrons in the conduction band of metals are relatively free to be driven by an EMF applied to the metal.

    And whether a device is primarily driven by current or voltage, and whether the device is polar or not (LED versus a resistor), just depends on the device itself.
  6. Aug 18, 2009 #5
    I understand the classical model completely, I know all about Latice collisions and phonons and even about LEDs (a PN junction by the way). I'm smart enough to use a search engine to find out how different electrical components work. None of those are my question.

    My question is much harder to find the answer to than any of those. Really, I'm looking for information on the most accurate model of electrical energy transmission in a circuit. Even Drude's model is too simple.

    I've run a across references to surface charges and poynting references, and it creates a model of energy transmission that I can believe and quantify, but it lacks a description of how the energy is actually received by devices. This isn't really a model, rather it is something that is proven and has been around since 1967, which is strange that none of my EE textbooks mention it... What I haven't been able to piece together is how devices use this energy, because it is flowing in from both directions...

    That has been my question. How the energy is actually SENT to devices, and how devices then get that energy.

    And by getting the energy I mean how does a resistor consume 10 watts of the total energy supplied by the battery? This is just an example, I know how this works in the classical model, but want I more concise generalization.
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