when a dielectric is introduced in b/w a charged capacitor..(capacitor not connected to a battery) which of the parameters change- charge , electric field , potential? and why ?also tell whether charge on capacitors remain same or not and why? (does the induced charges on dielectric changes the charges on capacitor)..?

Dear student,

If thickness of dielectric slab is less then distance between capacitor and if the length of slab is parallel to plate of capacitor then it is divided into three capacitor which are connected in parallel.
2 widout di electric and 1 with dielectric..

now apply C= E A/ d to get equivalent capacitence..
for capacitor wid dielectic then it is C= KEA / d..