My book says, in a non-uniform electric field, the dipole experiences both a torque and a force acting upon it while in a uniform electric field there is only torque ( no force).
My first doubt is that if torque is a kind of force only then what is this other force that acts upon the dipole when it is in a non-uniform field? And secondly, how can the net force be zero on the dipole in a uniform field?
In a uniform electric field, the net force on an electric dipole is zero because the force on opposite poles acts in opposite directions. But the torque is not zero as the forces are separated by a small distance. This causes rotational effect and the dipole tends to rotate until it aligns itself with the electric field i.e dipole moment and electric field vector are in same direction. Hope this helped.
When a dipole is placed in a uniform electric field the force on positive charge and negative charge are equal and opposite since the field is uniform and charge is same in magnitude present on them.but there exists some torque due to some separation between equal and opposite forces.in case of non uniform field the force acting on the charges may not be same then there may be a force acting on dipole itself because there the forces acting on the charges need not be equal and opposite and there may or may not be torque. It actually depends on situation and the conditions given for the field. Hope it helps you.
