dipole

Question 1

the dipole has its least potential energy when ….

Answer 1

it is in its equilibrium orientation,which is when its moment p(vector) is lined up with the field E(vector)

Question 2

the previous choose the potential energy to be zero when ….

Answer 2

the angle θ is 90°

Question 3

the potential energy U of the dipole at any other value of θ can be found by

Answer 3

calculating the work W done by the field on the dipole when the dipole is rotated to that value of θ from 90°
U = -W = - f (90° to θ) t dθ = f (90° to θ) (p E sinθ) dθ
= -pEcosθ
U = - p·E

Question 4

the dipole is torqued into

Answer 4

p line up with field E

Question 5

net torque(扭矩)(扭轉的力矩) on dipole in an electric field

Answer 5

the net torque on dipole τ = Fх sinθ + F (d - х) sinθ
= Fd sinθ
= p E sinθ
= p × E
θ = angle between d and E
the dipole p is torqued into alignment with E