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Math Help - electrical problem

  1. #1
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    electrical problem

    Four 18 W lamps are connected in parallel across 6V. Draw the circuit.

    What is the current through each lamp? What is the resistance of each?

    What is effective resistance of the combined four lamps?

    Please help with this problem.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by rcmango View Post
    Four 18 W lamps are connected in parallel across 6V. Draw the circuit.

    What is the current through each lamp? What is the resistance of each?

    What is effective resistance of the combined four lamps?

    Please help with this problem.
    See attachment.

    The voltage accross each lamp is the same and 6V. So the current through
    eash lamp is given by P = IV, here 18 = I.6, so I = 3 Amps.

    Ohms law for a single lamp tells us that V=IR, so R=18/3 = 6 Ohms.

    The total current supplied by the battery is 4 times the current through the
    individual bulbs, so is 12 Amps. Now apply Ohm's law to the entire circuit to
    get: 18 = 12.R, so R=1.5 Ohms is the resistence of the combined four lamps.

    RonL
    Attached Thumbnails Attached Thumbnails electrical problem-gash.jpg  
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  3. #3
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    excellent diagram, thats how i was seein it. THankyou.
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