Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Dipole torque problem Help please

  1. Apr 16, 2007 #1
    dipole torque problem.. Help please!!!

    Hi, the problem is:

    Show that if the force action on a dipole p placed in an Non uniform electric field is [tex]p\cdot \nabla E_{ext}[/tex], the torque acting on the dipole in this field is

    [tex]\tau =r \times (p\cdot\nabla E_{ext})+p\times E_{ext}[/tex]

    where r is the vector distance to the dipole from the point about which the torque is to be measured.

    How can i do this??? it's urgent.. please!!!
  2. jcsd
  3. Apr 17, 2007 #2

    Meir Achuz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The first term is just rXF.
    The second term is the torque due to the couple acting on the dipole.
    You can get that torque by usilng the couple acting on +q and -q charges
    a distance L apart, with p=qL.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook