To find out potential energy of a dipole

Question

If potential energy of a dipole is chosen to be zero when dipole mement makes pi/3 with uniform electric field E then potential energy when dipole moment vector becomes parallel to the electric field will become 

Answer 1

Hi Shubhangi!

 

Starting with the expression for the potential energy of an electric dipole in an external electric field:

 

U = -pEcos(θ)

 

where

 

p = electric dipole moment magnitude

E = electric field magnitude

θ = angle between dipole direction and field direction

 

we can see that the difference in energy between when the dipole is parallel to the field and when it is at an angle of (π/3) radians with respect to the field is:

 

ΔU = U₀ - U_π/3 = -pEcos(0) - (-pEcos(π/3)) = -pE - (-pE(0.5)) = -pE + (0.5)pE = -(0.5)pE

 

Hence, if U_π/3 is taken to be 0, then U₀ must still be -(0.5pE) below it; thus at -(0.5)pE.

 

I hope this helps!  Just let me know if you have more questions about this, or any other problems.