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!

Electromagnetism, current in coil

  1. Jun 2, 2013 #1
    1. A coil of 25 turns of wire is suspended by a thread. When a current flows through the coil, the tension in the thread is reduced by 4.0 x 10-2 N. What are the magnitude and direction of the current? {magnitude of current; direction of current}

    a) 4.1 A; clockwise
    b) 0.16 A; clockwise
    c) 0.16 A; counter-clockwise
    d) 4.1 A; counter-clockwise



    2. Relevant equations

    F=IlB
    B= [itex]\frac{\mu NI}{l}[/itex]

    3. The attempt at a solution

    B=[itex]\mu[/itex]NI/l
    F= IlB = Il([itex]\mu[/itex]NI/l) = I2[itex]\mu[/itex]N
    I = [itex]\sqrt{ \frac{F}{\mu N} }[/itex]

    so I = √4.0x10-2 / 4∏x10-7 x25 = 35.48A

    My answer doesn't match with any of theirs.

    Also, how would I find the direction of current? I don't know the direction of B (magnetic field).

    Any help would be greatly appreciated.
     
  2. jcsd
  3. Jun 3, 2013 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Show your reasoning - why would you expect that a current through the wire would decrease the tension in the thread?
     
  4. Jun 3, 2013 #3

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Just posting to get on the thread. Seems like there's a lot of info missing. Seems like this problem gives a whole new meaning to "pulling yourself up by the bootstraps"! :smile:
     
  5. Jun 3, 2013 #4
    Is there uniform circular motion involved?
     
  6. Jun 4, 2013 #5

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    You are the one with the whole problem statement in front of you, you tell me: is their uniform circular motion involved?
     
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: Electromagnetism, current in coil
  1. Current in a coil (Replies: 3)

Loading...