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What really is "energy" -- is it the amps or the wattage?

  1. Mar 16, 2017 #1
    If volts is only an "electro motive force", that is, it only pushes, and resistance is what tries to hold everything back, and "amperage", that is, current, is the actual electricity ( or not, that is my question ) and watts is the calculation of everything together and the total output, is it really just the amps that matter and the resistance and volts are just things in the way?

    If you had zero resistance and just 2 volts and 10 Amps that means it is almost like infinite energy and it would spread in all areas that have zero resistance, like ina vacuum? It may sound like a stupid question, but I have been reading about electronics as a hobby for a while and I really don't understand the deep relationship between these three factors, resistance, voltage and amps besides Ohms law and such.
     
  2. jcsd
  3. Mar 16, 2017 #2
    Wattage (joules/second) is a measure of work being done and is the product of the voltage across the load and the current through it. The voltage drives the current through the load, which causes the load to perform work, whatever that work may be.

    Also a vacuum would have infinite resistance (no electrical connection whatsoever) rather than zero resistance. You're describing a superconductor. Ohm's law would be essentially irrelevant if the resistance was infinite since Ohm's Law only applies to an actual circuit, and you can't complete a circuit through infinite resistance.

    Also there is no such thing as "infinite energy". In a superconductor, the current will not diminish due to resistance (at least not by any significant amount in a significant amount of time; yes I know these are non-exact terms and I apologize), but the energy in the circuit will never exceed that which you put into it.
     
  4. Mar 16, 2017 #3
    Thanks for enlightening me about the electrical resistance in vacuum, though load and work are relative terms, but still...

    I have read somewhere that for example in an ocurrence of a static electricity phenomenon, it is the amps that hurt and not the volts, so while 10 volts and 3000mA and 1000 Volts and 30 mA have the same wattage, if you are hit by 10V x 3A you wouldn't survive, but it will be harder for that to happen because of the lesser voltage, and 1000 volts with 0.03 A will likely shock easily but it will only result in a minor injury each time, so, to me it seems like current ( amps ) is the real "power" and calculating wattage is only a practice that is convenient when making circuits and considering each component.
     
  5. Mar 16, 2017 #4

    analogdesign

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    The "power" is the watts. Like XZ923, it is Joules/sec. Joules is an energy.

    The amps is what kills you because that is a measure of charge carriers per time. Voltage is more a potential energy. It can kill you if it can deliver the current, but when your hair stands up after rubbing a balloon, obviously the high voltage isn't hurting you.

    People on here hate water analogies, but if you think of volts as pressure and current as flow a lot of things make sense. A huge amount of water without any pressure (high amps, low volts) will drown you, but a rain drop (falls from a great height, but very little flow) doesn't hurt you.

    Don't get mixed up yet with terms like "energy". It has a specific meaning. In electrical terms, an energy of 1 Joule is a One Coulomb capacitor charged up to one volt. You can calculate how many electrons that is.
     
  6. Mar 16, 2017 #5
    Ok it makes sense now, I have now cleared the confusion, thanks to you both!​
     
  7. Mar 16, 2017 #6
    Technically they both hurt; one doesn't exist without the other. To use a somewhat morbid analogy, imagine a boulder perched on the edge of a cliff. It has potential energy but as long as it's not moving there's no kinetic energy. If the boulder gets pushed off the cliff and you're under it, it will hurt, the same way an electric shock will hurt (or kill). The boulder is what physically hits you; gravity is the force causing it to hit you. With electricity, amperage is the measure of the actual current, voltage is the force driving it.
     
  8. Mar 16, 2017 #7

    phinds

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    Impossible. The human body will not draw anywhere NEAR 3amps at 10v. In fact it will draw so little you won't even feel it unless you are using your tongue on the voltage terminals.

    I'm not positive but I'm pretty sure that would kill you. Again, you don't get "hit with 1000 volts at 30 milliamps", you get hit with 1000 volts and your body will draw whatever current is appropriate for its resistance. I think that at 1000 volts, even if the supply is limited to 30milliamps, it would kill you.
     
  9. Mar 16, 2017 #8

    davenn

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    Phinds answered your comment correctly

    you have the same misunderstanding that so many posting on here do
    consider a 12V car battery, capable of supplying 300A + and you can touch both terminals and not feel a thing

    it is the resistance of the load .... you or other circuit and the voltage across that load that determines the current that flows
    this is regardless of if the power supply can supply 10A or 1000A


    Dave
     
  10. Mar 19, 2017 #9

    David Lewis

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    EMF tells you how concentrated the energy is in a given amount of electricity.
    The force that does the pushing is electrostatic force.
    Current is electricity in motion. Electricity itself arises from the surplus/deficit of charge.
    Or how fast work is being done.
     
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