For an electric dipole in a non-uniform electric field with dipole moment parallel to direction of the field, the force F and torque τ on the dipole respectively are ____________.
Fill in the blank with the correct answer from the options given below.
1
F = 0, τ = 0
2
F ≠ 0, τ = 0
3
F = 0, τ ≠ 0
4
F ≠ 0, τ ≠ 0