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Homework Help: Electrical= Resistance and Energy

  1. Feb 1, 2007 #1
    A wire of resistance 9.0 is connected to a battery whose emf is 3.0 V and whose internal resistance is 1.0 .
    (a) How much energy is transferred from chemical to electrical form in 4.0 min?
    (b) How much energy appears in the wire as thermal energy in that time?

    answer to a= 216 (that's correct)
    for b, i got 189.629 (that one is wrong though)

    For the work, i did: I= 3V/9 = .3333 A
    Vtotal= 3V-IR
    Vtotal= 3V-.333(1)
    Vtotal= 2.6666
    p=Vsquared/R
    P=2.666 squared/9
    P= .79011
    .79011 (4) (60) = 189.62
     
  2. jcsd
  3. Feb 1, 2007 #2
    When calculating the current -- why would you ignore the resistance of the battery? (Normally you would, but in this case it is a fairly high component of the overall resistance of the circuit)
     
  4. Feb 1, 2007 #3
    i would ignore it because its asking for the energy in the wire specifically..i believe anyway
     
  5. Feb 1, 2007 #4
    if for a new answer, i got 194.4 joules..would that be correct?
     
  6. Feb 1, 2007 #5
    is 194.4 the answer?
     
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