1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Torque on a current loop about a hinge line

  1. Nov 20, 2009 #1
    1. The problem statement, all variables and given/known data

    A rectangular 20 turn loop that is 12 by 5 cm carries a current of 0.10A. It's hinged at one of the longer 12cm sides. It's mounted with its plane at an angle of 33 degrees to the direction of a magnetic field of 0.50T. What's the torque about the hinge line?

    2. Relevant equations

    T = iAbsin(theta)

    3. The attempt at a solution

    I guess my question is about the significance on the hinge line. The example in my book hinges on the z axis located in the middle of loop, so it uses the formula:

    t = 2iaB (b/2) sin (theta)
    where b/2 sin(theta) is decribed as the "moment arm". When it is hinged on the left longer side instead of the z axis, does this mean the equation would become 2iaB b sin (theta) instead?
  2. jcsd
  3. Nov 20, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi theowne ! :smile:

    (have a theta: θ :wink:)
    There's various ways of looking a this (including actually working it out from scratch :wink:), but the easiest is probably to add a second loop next to the first, making one big loop with a hinge in the middle! :smile:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook