Question

when will the torque acting on the electric dipole will be maximum n minimum

Answer 1

formula, of Torque = PEsin∅
where P is dipole moment
E is electric field
and ∅ is the angle dipole and Electric field .

now ,
T = P.Esin∅
Torque maximum when , sin∅→ max
we know max value of sin∅ = 1 at ∅ = π/2

so, max T = P.E

and minimum when sin∅ = -1 at ∅ = -π/2
e.g min T = -P.E

Answer 2

when minus cos theta is 180 degree it is maximum

when minus cos theta 0 degree it is minimum