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!

Find the force between two wires

Tags:
  1. Mar 23, 2016 #1
    1. The problem statement, all variables and given/known data
    Two rectilinear wires with length 100 m have the intensity 2 A. The wires in are perpendicular directions with distance 5 meters from each-other. Find the force they interact.

    2. Relevant equations
    F=(I1*I2*μ0*l)/(2*pi*d)
    3. The attempt at a solution
    F=(2*2*4*pi*10^-7*1)/(2*3.14*5)=1.6*10^-7
    The solution in my book is 0 N.
     
  2. jcsd
  3. Mar 23, 2016 #2

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Check the direction of the magnetic fields and the direction of the currents...
     
  4. Mar 23, 2016 #3
    I think the currents are perpendicular with each other and so are the vectors of magnetic induction.
     
  5. Mar 23, 2016 #4

    berkeman

    User Avatar

    Staff: Mentor

    Yep. So what force would that generate?
     
  6. Mar 23, 2016 #5
    I can't find an argument for that.
     
  7. Mar 23, 2016 #6

    berkeman

    User Avatar

    Staff: Mentor

    Okay, so I'm getting the impression that you have not been exposed to the vector relationship between the current in a wire and the B-field that circulates around it, is that right? Also, have you learned how to calculate the vector Lorentz Force?
     
  8. Mar 23, 2016 #7
    I don't know what the Lorentz Force is. I know that F=B(induction)*l(length)*I(intensity)*sin alpha. I also know that the force is perpendicular with current and induction
     
  9. Mar 23, 2016 #8

    berkeman

    User Avatar

    Staff: Mentor

    Do they have any diagrams in your textbook that show a current carrying wire and the B-field circling around the wire? Do they discuss and show the "Right Hand Rule" for the direction of the B-field? I'm just trying to get a feel for how the book wants you to know how to answer this question...
     
  10. Mar 23, 2016 #9
    Yes. I have learnt the Right Hand Rule. Actually I am doing some problems that are not from the book I'm studying and I don't know which is appropriate for me to do with the knowledge I have so far.
     
  11. Mar 23, 2016 #10

    berkeman

    User Avatar

    Staff: Mentor

    Ah, that might explain it. Yeah, just using the force formula for parallel wires will not work for perpendicular wires.

    The B-field for a current carrying wire looks like this:

    http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html#c1
    magcur.gif

    And the Lorentz Force is written as the cross product of two vectors: F = qv X B Where F is the force vector, v is the velocity vector of a charge, and B is the magnetic field vector. Vectors have both a Magnitude and a Direction.

    The vector cross product can be simplified if you are not familiar with it, so the Lorentz force can be re-written as magnitudes only F = qvB sin(θ), where θ is the angle between the velocity vector v and the magnetic field vector B. So the result of the cross product is maximized when v and B are in the same (or opposite) direction, and it is zero when they are perpendicular.

    Does that help some? You can do more reading about this at Hyperphysics or Wikipedia. :smile:

    Edit -- not sure why the image is not displaying correctly, but you can click on the link to see it.
     
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: Find the force between two wires
Loading...