What is the orientation of the dipole for minimum torque?
Answers
A2A
τ⃗ =m⃗ \crossE⃗ ⟹τ⃗ =mEsin(θ)n^
There are positions for stability according to this equation, one is when the electric field and the electric dipole are parallel, while the other is when they are anti-parallel.
The unstable one is when they are antiparallel because from the equation U=−m⃗ ⋅E⃗ ⟹U=−mEcos(θ).
At anti-parallel, the potential energy is positive. Bodies don't like to have positive potential energy, so even if the torque is zero, the potential is high which the body does not like and hence can be termed to be in "unstable equilibrium"
At parallel, the potential is as negative as it gets and the body likes that, plus the torque acting on it is also zero, so the position is termed "stable equilibrium".
Answer:
The torque on the dipole is zero, i.e., there is no rotatory motion of dipole. The resultant force on dipole is zero, i.e., there is no translatory motion of dipole. The potential energy of dipole is minimum