1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Energy of a Dipole in a Constant E Field

  1. Sep 7, 2009 #1
    1. The problem statement, all variables and given/known data
    The graph shows the potential energy of an electric dipole which is in a constant electric field; only the electric force is acting on the dipole. Consider a dipole that oscillates between plus and minus 65 degrees.


    a) What is the dipole's mechanical energy?
    b) What is the dipole's kinetic energy when it is aligned with the electric field?

    2. Relevant equations
    U = -pEcos[tex]\theta[/tex]

    3. The attempt at a solution
    I know that when the graph is at the trough it's -pE and at it's peak it's +pE. But I don't know how to factor in the 65 degrees. Please help!
  2. jcsd
  3. Sep 7, 2009 #2


    User Avatar
    Homework Helper

    At 180 degrees U = 2 μJ. Substitute in the relevant equation and find pE.
    At θ = 0, all the potential energy in converted to K.E. Similarly you can find P.E. at 65 degrees by substituting the value of pE and θ in the equation.
  4. Sep 7, 2009 #3
    Thank you so much! That really cleared it up for me!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook