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Electromagnetic Induction (Flux linkage)

  1. Apr 13, 2009 #1
    Apologies for numerous posts today, I'm trying to catch up from work I missed last term, and my uni is on holiday at the moment so cant get help from lecturers.

    I've been set the following which I think I've got correct, but not 100%. Am I right in calculating the area in m2?

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

    2. A rectangular coil measuring 20mm by 35mm and having 650 turns is rotating about a horizontal axis which is at right angles to a uniform magnetic field of flux density 2.5x10-3T. The plane of the coil makes an angle θ with the vertical, as shown in the diagrams.


    (i) State the value of θ when the magnetic flux through the coil is a minimum.
    (ii) Calculate the magnetic flux passing through the coil when θ is 30o.
    (iii) What is the maximum flux linkage through the coil as it rotates?


    2. Relevant equations

    ΔΦ=NBAsinθ

    3. The attempt at a solution

    i) Φ is at a minimum when θ=0

    ii) ΔΦ=650x(2.5x10-3)x(0.002x0.0035)sin30

    =1.365x10-5sin30

    =5.6875x10-6Wb

    iii) Flux linkage is maximum when θ=90

    ΔΦ=1.375x10-5sin90

    =1.375x10-5Wb

    Thanks,
     
  2. jcsd
  3. Apr 13, 2009 #2

    Cyosis

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    Homework Helper

    Almost, 1 m = 1000 mm, so 20 mm =20*10^-3m=0.02m. So you're a factor 100 off regarding the area.
     
  4. Apr 13, 2009 #3
    3. The attempt at a solution

    i) Φ is at a minimum when θ=0

    ii) ΔΦ=650x(2.5x10-3)x(0.02x0.035)sin30

    =1.1375x10-3sin30

    =5.6875x10-4Wb

    iii) Flux linkage is maximum when θ=90

    ΔΦ=1.1375x10-3sin90

    =1.1375x10-3Wb

    -----------------

    Ah, that was careless of me! Thanks for pointing it out. Is everything now correct. Am I right with my assumptions of min when θ=0 and max when θ=90?

    Thanks,
     
  5. Apr 13, 2009 #4

    Cyosis

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    Homework Helper

    Yes everything seems to be correct now. Your assumptions are easy to check. When theta is 0 the coil is parallel to the magnetic field so no field lines pass through the coil. When theta is 90 degrees the coil is perpendicular to the magnetic field and a maximum amount of field lines go through the coil.
     
  6. Apr 13, 2009 #5
    That brilliant. Thanks again.
     
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