An electric dipole is placed in a uniform electric field in such a way that its axis lies along the electric field. Does any force or torque act on the dipole?

Explanation

When an electric dipole is placed along a uniform electric field force acting on +q of the dipole is qE along the direction of `vec(E)` and force acting on -q is qE in the opposite direction of `vec(E)` [Fig.2.74]. So the resultant force on the dipole `=qvec(E)-qvec(E)=0` Since the the two equal forces act along the same line, they cannot produce a torque. So in this case, neither a force nor a torque acts on the dipole.