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Circuit Analysis Question

  1. Jan 23, 2006 #1
    A MP3 player is powered by a 6V battery pack that can supply 600mA-hr of current. If the MP3 player draws 30 mA of current, how long will the battery last before it needs recharging? and What is the power used by the MP3 player?

    if any1 can help i'd appreciate it
  2. jcsd
  3. Jan 23, 2006 #2


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    Staff: Mentor

    If a battery has a 1A-hr capacity, and you draw 1A from it, how long will it last? Also, do you know the formula for calculating power from voltage and current?
  4. Jan 23, 2006 #3
    it would last 1-hr. isnt the formula for power current over voltage???
  5. Jan 23, 2006 #4


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    Science Advisor
    Gold Member

    Ummm, no. The formula for power is Volts x Amps = Watts.
  6. Jan 23, 2006 #5
    ok thanx .............
  7. Jan 24, 2006 #6
    t = 600 mA-hr/30 mA = 20 Hours (optimistic, but theoretically correct)
    P = .03A x 6V = .18 Watts (as long as the battery holds at 6 Volts)
    E = .18W x 20Hr x 3600 sec/hr = 12,960 Watt-seconds (Joules)
    Practically, the battery won't hold at 6 volts during the phases of its discharge, so the above calculations are only the ideal case.
    -Dr. Bob
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