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Force on an electric dipole

  • Thread starter wam_mi
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Homework Statement



A dipole, consisting of a charge -q at position vector r and a charge +q at position vector r+s, is sitting in an external electric field E(ext).

(a) Write down the total force on the dipole F(dipole) due to the external field

(b) Show that when s is small,
F(dipole) approx. = (dot product of p and del operator)*E(ext)
where p is the electric dipole moment, p = q s

(c) In what limit does the result become exact?


Homework Equations



p = q s
F = torque = cross product (p and E(ext))

The Attempt at a Solution



(a) F(dipole) = cross product (p and E(ext)) = q* cross product (s and E(ext))

stuck on (b) and (c)


Please help!
 

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