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Magnetic energy

  1. Nov 21, 2009 #1
    1. The problem statement, all variables and given/known data
    Considering the earth magnetic field, I need to find the magnetic energy stored in our classroom.


    2. Relevant equations

    U= (1/2*[tex]\mu[/tex]) B2

    3. The attempt at a solution

    Any suggestions?
     
  2. jcsd
  3. Nov 21, 2009 #2

    kuruman

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    Your expression is the energy density (Joules/m3). How many cubic meters is the volume of your classroom?
     
  4. Nov 22, 2009 #3
    around 300 cubic meters
     
  5. Nov 22, 2009 #4

    ideasrule

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    Do you still need help? You can find the value of B online, so you can find the energy density using your formula.
     
  6. Nov 22, 2009 #5
    so once I have B i just put in the equation and solve for U

    and then I multiply U by the volume of the classroom?


    where do I found accurate value of the magnetic field of the Earth online?
     
  7. Nov 22, 2009 #6

    kuruman

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  8. Nov 22, 2009 #7
    U= (1/8*pi*10^-7 ) *(54,191.9 nT )^2 = 0.001168500483 (J/m^3)

    now

    U*Volume= Energy classroom = 0.00117 (J/m^3)* 300 = .35 Joule

    is this right?
     
  9. Nov 22, 2009 #8

    kuruman

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    I didn't put in the numbers, but it looks right.
     
  10. Nov 23, 2009 #9
    thank you
     
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