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  1. Dec 4, 2013 #1

    dwn

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    1. The problem statement, all variables and given/known data

    A coil with an inductance of 2.0 H and a resistance of 10 ohm is suddenly connected to an ideal battery with E = 100 V. At 0.10 s after the connection is made, what is the rate at which:

    (a) energy is being stored in the magnetic field, ans: 2.4*102
    (b) thermal energy is appearing in the resistance, and ans: 1.5*102
    (c) energy is being delivered by the battery? ans: 3.9*102

    2. Relevant equations

    UL=.5LI2
    VR=E(1-e-t/tau)

    3. The attempt at a solution

    V=IR 100/10 = I = 10 A
    UL= .5*2*102 = 100

    Clearly I'm missing a step or another equation to derive the current because I don't believe 10 A is correct. Please advise!
     
  2. jcsd
  3. Dec 4, 2013 #2

    ehild

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    Homework Helper
    Gold Member

    10 A is the current after infinite time, and it is equal to Io= E/R. (E is the emf of the battery)

    The current changes according to the function I=Io(1-e-t/τ).

    You need to calculate the rate of changes of energies at t= 10 s.

    ehild
     
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