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Homework Help: Human powered charger

  1. Aug 7, 2010 #1
    1. The problem statement, all variables and given/known data

    Can some one please help me out on this, i cant seem to get my head around it.

  2. jcsd
  3. Aug 7, 2010 #2
    tell me what you've done so far.
  4. Aug 7, 2010 #3
    do you know the equation for efficiency? if not, do you think you can derive it? if a system were 0 percent efficient(0.00), you'd need to supply infinite energy to reach any finite stored energy. If the system were 100% efficient (1.00), you'd need to supply Z joules to store Z joules. Can you think of a relationship between P_in and P_stored that relies on the 0 to 1.00 representation of efficiency that would produce the end behavior we just explored?
  5. Aug 12, 2010 #4
    Hi Sorry about the late reply i have been away.
    I have not managed to do any thing on this question it has stumped me from he start.
    It says a human power charger is used but not what charger so i am assuming i can make on up? for instance a bike powered charger?
    Any info to get me started would help me a lot.
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