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Homework Help: Help with yr11 magnetic fields

  1. Oct 17, 2013 #1
    1. The problem statement, all variables and given/known data
    The diagram shows the magnetic field between like magnetic poles

    2. Relevant equations
    Point C is the exact middle of the region between the poles. Explain why the strength of the magnetic field at point C is zero?

    3. The attempt at a solution
    The like poles repel each other. In the center the magnetic fields are strongest and will be equal to each other? So they cancel out??

    *Please I have only just started learning about Magnetic fields in class and I have tried looking this up but cannot seem to get the answer/ explanation
  2. jcsd
  3. Oct 17, 2013 #2


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    Hi JenL! :smile:
    But why will they be equal to each other? :wink:

    (Even if you think it's obvious, you have to give a reason)

    btw, do you know about vectors?

    do you know how vectors add (and when they add to zero)?​
  4. Oct 18, 2013 #3
    I asked one of my classmates and is it because in the center there are no magnetic fields lines? (in the diagrams there are no magnetic field lines in the center) so the center's magnetic field strength is 0.
    I have learnt about vectors in forces but I am not sure if that if the same?
  5. Oct 18, 2013 #4


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    the field lines are a way of picturing the forces

    force is a vector, so it has a magnitude (a strength) and a direction

    the force at a point can be represented by an arrow at that point: the direction of the arrow shows the direction of the force, and the length of the arrow shows the strength of the force (at that point)

    so one way of picturing a force field is by drawing little arrows (nearly) all over it

    however, that can be confusing (if you've ever seen one, you'll know why)

    so instead we join some of the arrows together, making very long (and curved) arrows … these are the field lines

    the direction (the tangent) of the field line at any point shows the direction of the force at that point, and the magnitude is shown by how close together the lines are (because we lost the information of the length of the little arrows when we joined them up! :wink:)​

    see also http://en.wikipedia.org/wiki/Field_Lines
    i think the best way of answering the question (about the strength of the magnetic field at the midpoint) is to remember that the strength is the strength of a vector, and every vector must have a direction (unless its strength is zero) …

    so which direction would the vector point in? :smile:
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