a dielectric is introduced between the elements of the condenser kept at constant potential difference.then the charge on the condenser will increase or decrease.
when the potential is constant, and a dielectric slab is introduced, the capacitance increases and hence the charge increases.
Remember Cedric. Remember, if the time should come when you have to make a choice between what is right and what is easy, remember what happened to a boy who was good, and kind, and brave, because he strayed across the path of Lord Voldemort. Remember Cedric Diggory.
Albus Dumbledore
Goblet of Fire, Chapter 37, Page 724