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Math Help - Electrical power

  1. #1
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    Electrical power

    Which requires the most electrical power during operation?

    1. A 12 volt motor requiring 8 amperes.
    2. Four 30 watt lamps in a 12 volt parallel circuit.
    3. Two lights requiring 3 amperes each in a 24 volt parallel system.
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  2. #2
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    Quote Originally Posted by Raul780 View Post
    Which requires the most electrical power during operation?

    1. A 12 volt motor requiring 8 amperes.
    2. Four 30 watt lamps in a 12 volt parallel circuit.
    3. Two lights requiring 3 amperes each in a 24 volt parallel system.
    Power = Potential Difference x Current

    P = VI = I^2R = \frac{V^2}{R}
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  3. #3
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    answer?

    Hello Raul: see if this helps:

    for case 1, power P =V(volts)* I(amperes), P = 12*8=96W

    for case 2, you have to determine whether you can use any of the three Ohms Law formulas for power: P=VI, P=V^2/R, P=I^2*R. Because you are only given one measurement, the voltage V, and I is not defined, and R is not defined, you cannot find the total power with Ohms Law. The answer is allready given in implied form:

    total Watts = P = (30W + 30W + 30W + 30W) =120W

    for case 3 you have two measurements and so can use
    P = VI for each bulb: P=24*3=72W per bulb, since you have two bulbs the total P = 2(24*3)= 144W.

    The most power is used in case 3.
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  4. #4
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    Quote Originally Posted by Raul780 View Post
    Which requires the most electrical power during operation?

    1. A 12 volt motor requiring 8 amperes.
    2. Four 30 watt lamps in a 12 volt parallel circuit.
    3. Two lights requiring 3 amperes each in a 24 volt parallel system.
    1. 8 amps through 12 volts

    2. 4 x 30 watt lamps = 120 watts

    3. 3 x 2 amps=6 amps through 24 volts (the lamps are in parallel so each is drawing 3 amps)

    CB
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