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Homework Help: Average current produced by pacemaker

  1. Feb 9, 2010 #1
    1. The problem statement, all variables and given/known data
    Pacemakers designed for long-term use commonly employ a lithium-iodine battery capable of supplying 0.42 A*h of charge.
    b) If the average current produced by the pacemaker is 5.6 uA what is the expected lifetime of the device?

    2. Relevant equations

    C = A/s

    3. The attempt at a solution
    I solved for s. s = C/A = 5.6e6A (not sure if i converted that right) / .42 = 1.33e7 s. The thing is, I'm not sure how to convert this to years. thanks for the help
  2. jcsd
  3. Feb 9, 2010 #2


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    Homework Helper

    Re: Charges/Currents

    Life time = 0.42A*h/5.6*10^-6A =...........h.
  4. Feb 9, 2010 #3
    Re: Charges/Currents

    you cant convert seconds to years? You can do one of two things. Divide by seconds in a minute, divide by minutes in an hour, divide by hours in a day, then divide by days in a year. or you could search on google, "convert seconds to years" and then find the answer that way.
  5. Feb 9, 2010 #4
    Re: Charges/Currents

    yeah i can but i wasn't really sure if i did the first part right and used the correct equation in the first place
  6. Feb 9, 2010 #5
    Re: Charges/Currents

    ahh okay. i have no idea either
  7. Feb 9, 2010 #6


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    Homework Helper

    Re: Charges/Currents

    Capacity of battery is given in Ampere-hour.
    Therefore the life of the battery is given by (Ampere-hour)/ current drawn from the battery.
  8. Feb 9, 2010 #7
    Re: Charges/Currents

    im getting like 75000 yrs. that cant be right huh?
  9. Feb 9, 2010 #8


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    Re: Charges/Currents

    You know, if you keep the charge in amp-hours, it'll make things easier, because the time you calculate will automatically be in hours. All you have to do is convert the current from microamps to amps. This is easy, because a microamp is a millionth of an amp.

    current = charge/time

    ==> time = charge/current
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