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Difference between volt and current

  1. Sep 10, 2013 #1
    I've just been thinking about this for some reason and I realised I don't actually know... when you touch a live wire and you get electrocuted, is it the current or the voltage that gives you the zap? What causes the skin to burn when you touch it?

    I've seen electrical boxes that say 3,000 volts, can a person be killed or get serious harm from something with say 5 volts for example? Is there something I can plug into my electricity at home and set the amount of live electricity the comes out?

    I'm basically looking for something with a dial that allows me to control the voltage of electricity. Something like this http://www.dealschic.com/images/l/2992/1.jpg [Broken] but where I can set the voltage output myself.
     
    Last edited by a moderator: May 6, 2017
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  3. Sep 10, 2013 #2

    davenn

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    hi there :smile:

    this is a pretty common question you ask

    there's an old saying, Volts jolt, current kills and generally that holds true

    but its the mixture of the amounts of both that determine if you just get a good jolt or if you mite get electrocuted (killed)

    ~ 25 - 30 mA through the heart is enough to put it into fibrillation and if you are not attended to quickly you will die. But for that small amount of current to flow through your body, the voltage must be high enough to break down your skin resistance.
    The body can stand quite high voltage if the current is very low ... examples ...

    1) walking across the carpet and touching a metal door knob and that zap you feel can be as great as 10 - 15,000 Volts
    2) touching the bare sparkplug lead in your vehicle can hits you with ~ 25,000 Volts ... it REALLY jolts you
    3) Van de Graff generator many 10's of 1000's of Volts and you have lots of fun watching everyone's hair
    all stick out
    but on those examples the current is very low maybe 100's of uA to a few mA

    But when it comes to mains power 120/220VAC and higher, the current that the system is able to supply if very high, many Amps. and skin resistance is easily broken down and more so with the addition of a bit of perspiration.
    Generally 50V and up is deemed High Voltage and it to be treated with care

    Cheers
    Dave
     
  4. Sep 10, 2013 #3

    davenn

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    Ohhh forgot to comment on your last bit with the meter.

    the meter DOESNT control any voltage. It just reads the voltage that is present in a circuit, across a battery etc.

    for AC Voltages we use transformers to change Voltages from one level to another ... mite be low to higher or higher Voltage to a lower one.

    In DC Voltage circuits we can use regulator circuits ... these may be voltage regulator IC's like a LM317 or a LM7812 or =we can use discrete components ( no IC's)

    Yes, that's what your plugpack does ... for your battery charger for you mobile phone, laptop and a dozen other things around the home.
    Some plugpacks drop the voltage and then change it to DC, others may just drop the output to a lower AC Voltage


    cheers
    Dave
     
  5. Sep 10, 2013 #4

    Baluncore

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    Voltage is the pressure of the charge carriers.
    Current is the flow of charge carriers.
    Resistance limits the current.
    Current = Voltage / Resistance.
     
  6. Sep 10, 2013 #5

    meBigGuy

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    The current does the damage. The voltage is the force that pushes it through your skin resistance. If you connected a battery to two needles and broke through the skin, a low voltage would kill. When current goes through a resistance, it disspates power, so the current through your skin causes it to get hot.

    There are all sorts of things that convert home power into other forms or limit the flow. The most common converters are AC to DC power supplies (like wall warts, battery chargers), transformers, and AC to AC converters. Many of them are not adjustable. Technically a circuit breaker controls the maximum amount of current. A resistor limits the current. You asked a broad question with many different answers depending on what you are trying to accomplish.

    An adjustable power supply will convert your line voltage to adjustable low voltage DC. Like this http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2130343_-1. There are a wide range of power conversion systems, depending on your needs.
     
  7. Sep 11, 2013 #6
    ok a very crude example of something I'm looking for is this.

    5-Electrical-tester-with-OpenJaw-Current-Check-Voltage-Continuity-and-Current-600V-1000V-AC-Free.jpg

    I don't even know what this is and I'm pretty sure it just tests to see if something is live. But I want something that looks like that, where I can plug it into my socket at home, turn the dial to say 1mA and then when you touch the prong you will get a 1mA shock. Again ignore the image I just grabbed something that I thought such a device might look like
     
  8. Sep 11, 2013 #7

    phinds

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    This is just another meter like the first one you posted and meters MEASURE things, not control them.

    EDIT: that is, you are looking at meters in general, which is not what you want. Very expensive power supplies can be had that have a current-limit feature, as well as a voltage adjustment. To get something that feeds you wall socket voltage the way you want, you would need to build a current-limiting circuit.
     
  9. Sep 11, 2013 #8
    Thanks. I know the image is just a reader but hopefully that gave you a sort of idea of the thing I'm after. I just want something that allows me to set the voltage and amperage of the electricity flow so I can connect a peice of copper and now that copper wire carries the exact voltage and amperage that I set on the machine.
     
  10. Sep 11, 2013 #9

    phinds

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    You really need to study some basic electronics. A copper wire is a short circuit. It cannot have any voltage across it.
     
  11. Sep 11, 2013 #10
    I thought copper wire was the primary material for carrying a current? Anyway I'm not looking to learn about electronics I just want to create a very simple experiement.

    Also@MeBigGuy the machine one the website you linked http://www.jameco.com/webapp/wcs/st...30343_-1?avad=55963_a4f21477&source=Avantlink gives out amps, I need something like that but I need to be able to set it to milliamps. 0.1 - 10mA
     
  12. Sep 11, 2013 #11

    meBigGuy

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    You are asking questions that require us to teach you basic electronics. You need to understand voltage, current and resistance and how they relate conceptually (ohms law). At that point you might understand what a 10K resistor does and whether it is useful to you. You may also then understand what a power supply is, what a meter is, and what the meter measures.


    I don't think anyone here is really interested in providing more answers about how to shock people without killing them.
     
  13. Sep 12, 2013 #12
    Darwin award in the making. Dont put things in your socket and try to make anything that can give you a shock. If you want to get a shock, by a electrocuting flyswapper. They are harmless, and they will shock you.
     
  14. Oct 2, 2013 #13
    In regards to the original question I'd think that the "Hydraulic Analogy" is helpful in understand the relationships between volts/current/resistance.
     
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