1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Magnetic Field at the center of a square

  1. Jun 19, 2013 #1
    1. The problem statement, all variables and given/known data
    photo[1].jpg


    2. Relevant equations

    not sure

    3. The attempt at a solution

    I am not sure how to start this problem.
     
  2. jcsd
  3. Jun 19, 2013 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    I would start with Biot-Savart.
     
  4. Jun 19, 2013 #3
    You've probably seen how to obtain the field of a single line, whether through the Biot-Savart law or, more simply, through Ampere's law. Then just remember that the fields of individual components of a configuration add-up...
     
  5. Jun 20, 2013 #4
    So, would I use Ampere's Law for static magnetic fields?

    ƩB||Δl=μ0I ?
     
  6. Jun 20, 2013 #5

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Yes, since the wires are "long", you can use Ampere's law individually for each wire and then add the results vectorially.
     
  7. Jun 20, 2013 #6
    Ok, so I used ƩB||Δl=μ0I

    and got:

    ƩB||=3.8x10^-5
    ƩB||=4.3x10^-5
    ƩB||=5.0x10^-5
    ƩB||=3.0x10^-5

    For x,
    (3.8x10^-5)+(-5.0x10^-5)=-1.2x10^-5

    For y,
    (-4.3x10^-5)+(-3.0x10^-5)=-7.3x10^-5

    I have a feeling I didn't do this correctly...
     
  8. Jun 20, 2013 #7

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Let's take one wire at a time, and show all your work.
    For the wire carrying the 1.2A, write ampere's law and determine B at the center of the square.
     
  9. Jun 20, 2013 #8
    Ok, so I used ƩB||Δl=μ0I

    and got:

    ƩB||=[(4∏*10^-7T*m/A)(1.5A)]/0.05m
    ƩB||=3.8x10^-5

    ƩB||=[(4∏*10^-7T*m/A)(1.7A)]/0.05m
    ƩB||=4.3x10^-5

    ƩB||=[(4∏*10^-7T*m/A)(2.0A)]/0.05m
    ƩB||=5.0x10^-5

    ƩB||=[(4∏*10^-7T*m/A)(1.2A)]/0.05m
    ƩB||=3.0x10^-5
     
  10. Jun 20, 2013 #9
    Ampere's Law:
    ƩBΔl=μ0I

    ƩB(0.025m)=(4∏*10^-7)(1.5)

    ƩB=7.54x10^-5
     
  11. Jun 20, 2013 #10

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Ampere's law refers to the integration of a path around the current-carrying wire, i.e in this case you want the circumference, not the radius.
     
  12. Jun 20, 2013 #11
    ƩB(0.050m)=(4∏*10^-7)(1.5A)
    ƩB=3.77x10^-5

    ƩB(0.050m)=(4∏*10^-7)(1.7A)
    ƩB=4.27x10^-5

    ƩB(0.050m)=(4∏*10^-7)(2.0A)
    ƩB=5.03x10^-5

    ƩB(0.050m)=(4∏*10^-7)(1.2A)
    ƩB=3.02x10^-5
     
  13. Jun 20, 2013 #12
    Do I add these all together?
     
  14. Jun 20, 2013 #13

    rude man

    User Avatar
    Homework Helper
    Gold Member

    They were wrong before & are still wrong.
    In your post #9 you seemed to realize that the radius is 0.025m, not 0.05m. Now you're back to 0.05m?

    And you still haven't understood that the path of integration is not along the radius but the circumference.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Magnetic Field at the center of a square
Loading...