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Homework Help: Electromagnet help please?

  1. Aug 30, 2006 #1
    :surprised
    HI EVEYONE,
    NEED TO TAALK TO SOMEONE WHO IS UP ON CALCULATING THE VALUE OF (B), REQUIRED TO LIFT A PLATE OF XXNEWTONS. ALSO ESTIMATE THE M.M.F REQUIREDTO LIFT THE SAME PLATE.
    ANY TAKERS PLEASE?
    THANKS
     
  2. jcsd
  3. Aug 30, 2006 #2

    berkeman

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    Staff: Mentor

    No need to yell. What are the equations that describe the force generated by current flowing in a coil?
     
  4. Aug 30, 2006 #3
    Thanks For Your Reply.

    I WILL TRY EXPLAIN MY QUESTION AND PRESENT YOU WITH ALL THE FACTS I HAVE AT MY DISPOSAL.
    In the question it is first mentioned that the pull,P, exerted at each pole of the magnet is given by the equation:
    P = Bsquared x A divided by 2 x permeability of free space.
    A being CSA of the pole faces
    free space being 4 x pie x 10 to power of -7.

    OK.
    next we have c.s.a of magnet: 22 x 22 cm.
    R, radius: 0.5m.
    angle in degree`s: 120.
    relative permeability of magnet: 2000.
    relative permeability of plate: 1000.
    thickness of plate: 5cm
    weight of plate: 10'000 Newtons.


    I have drawn out a diagram to show you what the radius and angle are all about. Can i paste a paint document here? It would help a lot.
    Many thanks .
     
  5. Aug 30, 2006 #4
    just save the the jpeg file on your computer and then attach it to the post.
     
  6. Aug 31, 2006 #5
    electromagnet problem, need help please!

    View attachment electromagnet question.doc

    Q1, I need to calculate the value of B required to lift a plate.
    Q2, Estimate the mmf F required to lift the same plate.

    I understand P = B squared x A. divided by 2 x permeability of free space.

    This is what I have to work with:

    The plate to be lifted weighs, 10`000 Newtons
    Relative permeability of plate, 1000
    Thickness of plate, 5 cm.

    c.s.a. of magnet, 22 x 22 cm.
    radius (mean) of magnet, 0.5m ( shown as red circle)
    angle in degrees, 120.

    I am assuming you have to first calculate the distance between the 2 poles. Using the cosine rule I make it: 0.75metres.

    Now I need help with the rest please.
    I don’t just want the answer I want to understand the formula properly.

    Many thanks.
     
  7. Sep 3, 2006 #6

    Ouabache

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    Science Advisor
    Homework Helper

    Can you define more clearly, the units for each of the variables in your expression
    [tex]P = \frac{B^2 A}{2 \mu_o}[/tex]

    by the way, your expression looks similar to one I note on this page. Are you using the same units?

    From your given information, I don't see a value for "magnetic flux density" B. Perhaps you have some given information from which you can derive B.
     
    Last edited: Sep 4, 2006
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