A very small electric dipole with dipole moment p is placed in such in way that it is at a distance r from another point charge +q. The point charge lies on the axis of the dipole . Electric dipole moment is pointing towards the point charge. Determine electric dipole will attract the point charge or repel it ? What will be the magnitude of force between them ?

Explanation

Electric field on the axis of electric dipole is along the electric dipole moment , and so it will repel the positive charge. The magnitude of electric field intensity on the axis of dipole is :
`E=1/(4piepsilon_0)(2p)/r^3`
F=qE
`rArr F=1/(4piepsilon_0)(2pq)/r^3`