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Voltage and Amps

  1. Mar 22, 2008 #1
    What's the difference between volts and amps?
  2. jcsd
  3. Mar 22, 2008 #2
    If you can think of electrons flowing in a wire as water in a pipe, then pressure would be voltage, and flow of volume of water per second would be the current.

    Hope that helps.
  4. Mar 24, 2008 #3
    1 volt = 1 joule/coulomb = 1 weber/second.
    1 amp = 1 coulomb/second = 1 joule/weber.

    Voltage is electric potential/magnetic change rate.
    Current is electric change rate/magnetic potential.

    For detailed info, I'd recommend a peer-reviewed university-approved text on circuit theory, followed by e-m field theory as well as physics. The web has good info dispersed among the bad info. Those who are in the early stages of learning don't know the good from the bad. University libraries are still the most reliable source of info.

    My personal advice, no offense to anyone, is to completely AVOID water analogies. Current and voltage have a special relationship not found in water flow. Don't equate the two, as they vastly differ. A transformer is proof of that. Two circuits in close proximity couple, and current in circuit A and its associated magnetic field result in induction in circuit B, and vice-versa. Water flow and pressure do NOT exhibit this property. I'd advise all those who wish to learn circuits and fields to seek rigorous sources, and avoid these analogies like water flow/pressure.

    Just my 2 cents. Peace.
  5. Mar 26, 2008 #4
    Amps are proportional to the amount of electrons flowing per seconds (charge unit
    s per second)

    Volts are related to the amount of energy each electron carries (energy per charge unit)

    A normal PP3 (9V) battery:

    connect the positive and negative terminals together and the positive will attract electrons from the negative, so they will shoot across. As there is almost no resistance, they will do so very quickly, so a high current flows. Now put a resistor between the terminals instead, and they will flow slower - there is still a 9V difference between the two terminals, but as the electrons are flowing slower (due to the resistance), a smaller current will flow.

    Physically, a voltage gap represents the energy change on a group of electrons as they pass across it. A current represents the speed at which they pass across it.
    A fairly bad analogy follows...
    If you drop a cricket ball in air by 1m, it loses a certain amount of gravitational energy per mass unit. If you drop it in water by 1m, it will lose the same amount of gravitational energy, but fall at a lower speed, due to the resistance.
    Last edited: Mar 26, 2008
  6. Mar 26, 2008 #5
    Actually, you can do a transformer analog. The problem is getting ac water flow.
  7. Mar 26, 2008 #6
    What about water hammer?

    That sounds pretty ac to me... :eek:)

    And that wonderful hydraulic ram water pump is pretty ac too... :eek:) (I was always fascinated by one of those in my childhood, it was so mysterious).
  8. Mar 26, 2008 #7
    Please elaborate. If two water carrying closed tubes are in proximity, and one of them, "A", is actively driven by a pump, with ac flow, how does "induction" take place into "B"? Explain if you don't mind. I'm not aware of any, but by all means please share your thoughts with us. BR.
  9. Mar 26, 2008 #8
    Remember that sound? That was pulsating DC, but you're quite right that you can make a transformer analogy there, albeit with very poor regulation. After all, transformers can be made to work with pulsating DC I'm really impressed that there are many out there who know about water rams. I used to live near the Rife Ram and Pump Works. Thank you for the memory as well as a novel answer.
  10. Mar 26, 2008 #9
    Does it help if you think about it in terms of an equivalent circuit rather than in terms of induction?

    Oh, and I do pretty much agree with you about not using water analogies to explain electricity. I often use electricity analogies to explain pneumatics, however.
    Last edited: Mar 26, 2008
  11. Mar 27, 2008 #10
    tuned amplifier

    pls give anote and solved problem on it
  12. Mar 27, 2008 #11


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