While trying to solve this question: Photo copy of the question and answer:
Question:On charging a parallel plate capacitor to potential V the spacing between the plates is halved and a dielectric medium of E(permittivity)=10 is introduced between the plates without disconnecting the dc source. Explain using suitable expressions how the (i) capacitance(ii)electric field(iii) energy density of the capacitor change.
I couldn't understand the solution of (ii) part of Problem 31 question.
Why they wrote"The potential V remains constant even after the introduction of dielectric medium"? But the dielectric medium does interfere in the potential difference of the capacitor. right? Is there any mathematical explanation for this?
Also why in that (ii) part of the question they used V=EL formula and not E= σ/ε where σ=surface chatge density and ε=permittivity