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Find an expression for magnetic flux and calculate

  1. Jan 31, 2016 #1
    1. The problem statement, all variables and given/known data
    Loop of wire with the following properties in a magnetic field B. Find an expression for the magnetic flux through the loop and evaluate the magnetic flux at t=25s.
    The magnetic field is uniform but changes strength at time (t) given by
    B(t) = B0 exp (kt)


    Resistance = 20ohms
    Radius of loop = 10cm
    Angle of loop in magnetic field = 45 degrees
    B0 (constant) = 7.00x10^-2 T
    k (constant) = 0.250 s^-1


    2. Relevant equations
    Flux = AB cos theta
    Area of circle = Pi r^2


    3. The attempt at a solution
    So I'm working out B first from the function as:
    B(t) = 7.00x10^-2 T x exp x 0.250 s^-1 x 25s. = 1.189 T
    Area of loop = Pi x 0.10m^2 = 0.0314m^2
    Then using the flux equation with these values I get:
    0.0314 m^2 x 1.189 T x cos45 = 0.0264 Wb

    Is this correct? Thanks in advance
     
    Last edited by a moderator: Jan 31, 2016
  2. jcsd
  3. Jan 31, 2016 #2

    rude man

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  4. Jan 31, 2016 #3
    Sorry are you asking for clarification?
     
  5. Jan 31, 2016 #4
    e^(25 * .25) = e^6.25 = 518
    .07 * 518 = 36.3
    That differs considerably from the 1.19 that is shown for B.
     
  6. Jan 31, 2016 #5

    rude man

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    Sorry, didn't see the cos45 term.
     
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