Dipole torque problem Help please

  • #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!!!
 

Answers and Replies

  • #2
Meir Achuz
Science Advisor
Homework Helper
Gold Member
3,533
114
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.
 

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