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Understanding the relationship between Current, Voltage and Power (watts)

Discussion in 'Power Supplies' started by fasteddy, Dec 8, 2011.

  1. fasteddy

    fasteddy I have C.L.A.P Global Moderator

    Apr 26, 2010
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    Albion Park NSW
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    I got asked a question about current draw that I thought may be worth while sharing with others that may not have the understanding


    Is the calculation of 3.2 amps per 5m strip correct? I am running my entire display off one 20 amp breaker. 3.2a @ 12v per strip seems high. Just making sure I am not making a mistake. Mistakes happen to me a lot

    The Answer:

    Remember ohms law, the current goes up at the voltage goes down so you are thinking of 110v current draw which would be far less

    so 350 watts is 350 watts but the current draw changes depending on the voltage

    so current = power/voltage

    or power = voltage x current

    so a strip drawing 3.2 amps at 12vdc will draw about 39 to 40 watts

    so that equates to approx 0.4 amps per strip at 110V

    and 0.17 amps for 240v

    so you can run a fair few strips on one circuit

    I hope that helps a few who may not understand the relationship between Volatage, Current and Power
  2. David_AVD

    David_AVD Bite my shiny metal ass! Community Project Designer Generous Elf

    Jun 12, 2010
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    Victoria Point (Brisbane)
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