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Homework Help: Electromotive force

  1. Nov 10, 2009 #1
    1. The problem statement, all variables and given/known data

    Atorch battery transfers 5200J of chemical energy into electrical energy while supplying a current of 0.25A for 4400 s. The bulb transfers 4800 j of electrical energy into heat and light during this time. Calculate
    a)the charge that flows
    b)the e.m.f. of the battery
    c) the p.d. across the bulb
    d)the lost volts

    2. Relevant equations


    3. The attempt at a solution
    a) 0.25 x 4400 = 1100 C
    b)5200/1100 = 4.73V
    C) V=W/Q

  2. jcsd
  3. Nov 10, 2009 #2


    User Avatar

    Staff: Mentor

    Welcome to the PF.

    What does "p.d. across the bulb" mean? Power dissipated?

    If so, then power is just total energy divided by time, right?

    Once you have the bulb power, calculate the bulb voltage, and the difference between that and the battery source EMF is what is lost across the battery's internal resistance.
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