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Low Voltage Amps?

  • 24-11-2008 9:47am
    #1
    JOHNPT
    Closed Accounts Posts: 517 ✭✭✭


    Hi

    If power equals volts by amps then if I use low voltage downlights are they not using far more amps ant therefore far more expensive to run than 230 volt GU10 bulbs.

    50 watt low voltage bulbs would it not equal
    12 volt X 4.16 amps.

    Can anyone explain

    Thanks


Comments

  • #2
    jonnner
    Registered Users, Registered Users 2 Posts: 221 ✭✭jonnner


    You don't get charged for Amps you get charged for KiloWatts. Just because your using more current doesnt mean your using more power as your voltage has decreased.


  • #3
    Stoner
    Registered Users, Registered Users 2 Posts: 10,952 ✭✭✭✭Stoner


    you pay for power over time. KW hours

    Watt = current x voltage

    its the Watts / power you pay for so dont mind the curent

    4.16 Amps x 12 Vac = 50W
    0.227 Amps x 220 Vac = 50W

    The wattage is where your money goes, that's why people look for low wattage lamps for efficiency.


  • #4
    JOHNPT
    Closed Accounts Posts: 517 ✭✭✭JOHNPT


    So does a 12 watt low voltage bulb use the exact same power or cost the same to run as a Gu10 50 watt bulb?
    What about the transformer where does that come into the equation with regard cost of 50 watt low voltage bulbs


  • #5
    DublinDilbert
    Registered Users, Registered Users 2 Posts: 5,401 ✭✭✭DublinDilbert


    JOHNPT wrote: »
    So does a 12 watt low voltage bulb use the exact same power or cost the same to run as a Gu10 50 watt bulb?
    What about the transformer where does that come into the equation with regard cost of 50 watt low voltage bulbs


    Yes a 12V 50W bulb will use roughly the same amount of power as a 220V 50W bulb... they both use 50W..

    The transformer is the element which can take a high voltage / low current and covert to a low voltage high current.

    If you assume the transformer is 100% efficient, then Pin = Pout

    Remember P = VI

    With a transformer Vin x Iin = Vout x Iout

    Using stoners figures above:-

    4.16 Amps x 12 Vac = 0.227 Amps x 220 Vac = 50W


  • #6
    JOHNPT
    Closed Accounts Posts: 517 ✭✭✭JOHNPT


    O right I get it now. Thanks.
    Got one more question will post it in new thread


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  • #7
    fishdog
    Closed Accounts Posts: 1,113 ✭✭✭fishdog


    JOHNPT, I think what is important to realise is that although both lamps consume 50W and will cost the same to run the 12v lamp will produce far more light. I have been told 40% more light.


  • #8
    10-10-20
    Registered Users, Registered Users 2 Posts: 8,073 ✭✭✭10-10-20


    A guy once said to me that the wattage was the amount of heat output from the lamp and the light was 1% of that... :)

    True!


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