What does it mean when centres of charge coincide?

[AmKo3]

What does it mean when we say "centre of charges coincide"? What is the physical meaning of dipole moment?

 

[kuruman]

What does it mean when we say "centre of charges coincide"? [/QUOTE}
To answer this, more context is needed. I can only guess that you there are two or more charge distributions that have a "center of charge" just like mass distributions have a "center of mass". When they coincide, the centers are on top of one another.

What is the physical meaning of dipole moment?

The physical meaning is a collection of positive and negative charges such that the sum of positive and negative charges is zero, but the charges are spatially separated. An common example is the water molecule H₂O that is neutral (same total number of protons and electrons) but there is spatial separation of these charges. Free dipoles attract each other and this gives them interesting properties. Electric dipole attraction is important in protein folding for example.

 

[Kajal Sengupta]

What does it mean when we say "centre of charges coincide"? What is the physical meaning of dipole moment?

I guess you are referring to the explanation of polar and non-polar molecules required for explaining Polarization in dielectrics. If that is the case, then the meaning of "centers of charges coincide" is that the entire molecule is imagined to be like a rigid body . Now we know that in a rigid body the center of mass is the point where the entire mass of the body is supposed to be concentrated. Similarly in a molecule which has multiple charges of two kinds ( positive and negative) we imagine as if the centers of these charges are the points where the charges are concentrated. In absence of electric field these centers overlap on each other for non-polar molecules and are separated in polar molecules . Frankly speaking these are models to describe observed phenomena.