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What are the Adavantages of High Amperage?

  1. Jun 25, 2012 #1
    What are the advantages of having high amperage? By the way, I'm rather new to electronics.

    I know that having high-voltage reduces the energy loss through the wire, and you don't need as thick a wire. But I cannot find the advantages of high amperage on the internet. This may be due to my bad wording of the question, or due to my lack of knowledge on the subject, however I still would like to know.

    Thanks for any help, in advance.
     
  2. jcsd
  3. Jun 25, 2012 #2

    phinds

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    One example of where it is advantageous (a necessity really) to have high current (and very low voltage) is in electronic welding.

    It would be very dangerous to provide welding-level power using very much voltage, so typically (as I recall) welding is done with 3 volts and hundreds of amps.
     
  4. Jun 25, 2012 #3

    Drakkith

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    High currents are usually needed to provide high amounts of power to something. I don't really know if there's an "advantage" or not. I always thought of current as simply the consequence of your voltage and resistance.
     
  5. Jun 25, 2012 #4
    Thanks for the fast replies.

    Why is it dangerous to have high voltage in electronic welding? Is it so that the arc cannot travel far, or doesn't want to go through your body?
     
  6. Jun 25, 2012 #5

    marcusl

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    It's not so much a safety thing (welding is already plenty dangerous) but a property of the welding arc, which has very low resistance. Producing high power to melt the metal with a low resistance naturally requires high current and low voltage.
     
  7. Jun 25, 2012 #6

    Drakkith

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    I believe a higher voltage would increase the current even further.
     
  8. Jun 25, 2012 #7

    marcusl

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    Yes but there is an optimal current for each welding job. Factors include the type of metal to be welded and its thickness, the type of filler metal, the thickness of the filler rod, and the weld process used (e.g., TIG). Increase the current too far for the conditions and you produce lousy welds and/or melt too much of the metal. 50 - 200A are commonly used.
     
  9. Jun 26, 2012 #8
    The magnetic effect is proportional to the current, not the voltage so any application that depends upon the magnetic effect such as electric motors and induction cookers and furnaces are controlled by current.

    Electrochemical processes are current controlled so not only resistance welding but aluminium smelting, electroplating, battery charging etc.
     
  10. Jun 26, 2012 #9
    Oh, I didn't know that the magnetic effect relied on amperage. I thought it was just a higher charge in general, but this helps, as I have been interested in increasing the power of my solenoid.
     
  11. Jun 26, 2012 #10

    mfb

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    If you want to generate magnetic fields with coils, current (and geometry) is the important quantity. Voltage is just a nasty by-product required to power the coils, unless they are superconducting.
    As an example, the LHC uses superconducting coils with some kiloampere current in the cables. They produce a magnetic field of up to ~5T (design value is something like 9T).
     
  12. Jun 26, 2012 #11
    For transmitting energy, high amperages are a very bad idea due to joule effect.

    The advantage is generating a large amount of magnetic filed around it.
     
  13. Jun 26, 2012 #12

    Andrew Mason

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    The main reason for higher current is the need for lower voltage. For a vehicle even 100 volts would pose a significant safety hazard. The Prius uses just under 300 volts but only for the drive train functions which are heavily protected - the rest of the car uses 12 volts. If Henry Ford had used 100 volts in the Model T there would have been a lot of dead Ford owners who would not be coming back to buy another one.

    AM
     
  14. Jun 26, 2012 #13
    If the advantage of high voltage is that no thick wires are needed, then the advantage of high amperage should be that no thick electric insulation is needed.
     
  15. Jun 26, 2012 #14
    Why is high voltage more dangerous than high amperage?
     
  16. Jun 27, 2012 #15

    Andrew Mason

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    It is not. It's the amps that kills you. But in order to get high current to pass through you, you need high voltage. It is just Ohm's law. I = V/R.

    Study Ohm's law first and you will understand how voltage and current are related.

    AM
     
  17. Jun 27, 2012 #16

    phinds

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    While it is true that low voltage/high amperage wires require less insulation than the other way round, that is irrelevant to the reasons for USING them --- it's just a side effect.
     
  18. Jun 27, 2012 #17

    phinds

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    If you have a 10volt potential that is capable of delivering 1,000,000 amps, it will not hurt you at all to grab the leads, because low voltage won't actually USE much at all of that current capabiltiy on your high-resistance body.

    If you have a 10,000 volt potential that is capable of delivering a tenth of an amp and you grab the leads, it will most likely kill you because the high voltage will push enough current through your body to do so.
     
  19. Jun 27, 2012 #18

    Drakkith

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    If you look at Ohm's law, you will see that the current is determined by the voltage and resistance. When the resistance is very very low you can get a high current from even a low voltage source. However many things, such as the insulation around wires and human skin don't have low resistance. When you crank the voltage waaaay up it stars to have the ability to discharge through even high resistance objects. Once this happens you get very large currents through things that shouldn't have them. As Phinds said, a 10 volt source will not push a large current through your hands if you touch the leads, while a 10,000 volt source will.
     
  20. Jun 27, 2012 #19
    Only if the power source is constant voltage. With a constant current source, voltage is determined by current & resistance, but CCS is not how batteries & generators are designed. Insulators are very good, while conductors are not, so it is better to source constant voltage, i.e. the voltage is always full value, and the current varies from 0 to 100%, depending on loading.

    When current is determined by voltage & resistance, that is a man made condition. It's not Mother Nature. We could design the power grid so that I is constant, V varies with R. We don't for a good reason, but we could. Voltage does not "push" the current. I don't wish to be pedantic, but I feel this needs to be mentioned.

    Claude
     
  21. Jun 27, 2012 #20

    mfb

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    Well, the constant current source, attached to a human body (with high resistance), would have to deliver a high voltage. And, as stated before, this is bad for humans.
     
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