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Magnetic fields and current

  1. Aug 11, 2009 #1
    I'm trying to find out which logical statement is true.

    If and only if there is a region of space where there is no current, there cannot be a magnetic field that is both unidirectional and nonuniform.

    Or

    if there is a region of space where there is no current, there cannot be a magnetic field that is both unidirectional and nonuniform.

    Which statement is true????
     
  2. jcsd
  3. Aug 11, 2009 #2

    berkeman

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    Staff: Mentor

    What is the context for the question? Is it for schoolwork?

    What are the relevant equations for figuring this out? There are a couple of equations that relate current and magnetic field...
     
  4. Aug 11, 2009 #3
    aren't these two statements exactly the same?
     
  5. Aug 11, 2009 #4
    no, first statement is an equal sign. if and only if x then 5 means x=5

    second statement is an if and then statement. if x then 5 doesnt mean x=5 because if 5 then x cannot be concluded.

    2 statements are NOT logical the same.
     
  6. Aug 11, 2009 #5

    berkeman

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    Any answers?
     
  7. Aug 11, 2009 #6
    i'm using Ampere's law to investigate nonuniform unidirectional B fields.
     
  8. Aug 11, 2009 #7

    berkeman

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    Cool. So can you show us how to use Ampere's Law to start go answer your questions?
     
  9. Aug 11, 2009 #8
    i would draw a rectangular dL with 2 sides of the rectangle parallel and antiparallel to nonuniform and unidirectional B field lines.

    [tex] \oint \vec{B}\cdot \vec{dL} = \mu_{o} I_{enc}[/tex]

    where [tex] I_{enc} = 0 [/tex]
     
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