How much currect flows through wall outlet?

Discussion in 'General Electronics Chat' started by sensor, Sep 29, 2012.

  1. sensor

    Thread Starter New Member

    Sep 8, 2009
    18
    0
    I think, it's 220V AC from wall outlet.

    So how much current flows to bulb and fan from wall outlet?

    V = RI, P=VI

    What is the value of R (ohm) ? What is the value of P (power=Joul) ?
     
  2. sbixby

    Active Member

    May 8, 2010
    57
    10
    P=VI...

    For a 100W lightbulb --

    100W = 220V * I

    I = 100W/220V = 0.4545... A


    This is purely by the numbers, since a lightbulb's actual power usage will vary.
     
  3. sensor

    Thread Starter New Member

    Sep 8, 2009
    18
    0
    Where did you get the value of P (power) ?
     
  4. vpoko

    Member

    Jan 5, 2012
    258
    47
    It's on the light bulb. If you get a light bulb labeled 100W, it should use approximately 100W.

    More broadly, the amount of current that flows through an outlet is determined by the load. In this case it's 100W, but that depends on what's plugged in.
     
  5. sensor

    Thread Starter New Member

    Sep 8, 2009
    18
    0
    What do you mean by load?

    It's a bulb with 18W.
     
  6. vpoko

    Member

    Jan 5, 2012
    258
    47
    Load is the cumulative resistance of the entire circuit (not the sum of all resistors, but using the proper formulas for serial and parallel parts of the circuit). In a light bulb, it's already labeled for you. Since you know it's an 18W bulb, and you know the outlet is 220V, just plug those into your formula P=VI. 18=220*I. Now, to solve for I, divide both sides by 220. I=18/220=0.0818A.
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    The equation is simple.

    P = V x I

    18W = 220VAC x I

    The rest is algebra.

    BTW, light bulbs and many other appliances are measured in watts, not joules.
     
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