List - I List - II (I) Plates of an isolated, charged, parallel plate, air core capacitor are slowly pulled apart. (P) Electric energy stored inside capacitor increases in the process. (II) A dielectr

Question

List - I List - II (I) Plates of an isolated, charged, parallel plate, air core capacitor are slowly pulled apart. (P) Electric energy stored inside capacitor increases in the process. (II) A dielectric is slowly inserted inside an isolated and charged parallel plate air cored capacitor to completely fill the space between plates. (Q) Force between the two plates of the capacitor remain unchanged. (III) Plates of a parallel plate capacitor connected across a battery are slowly pulled apart. (R) Electric field in the region between plates remain unchanged. (IV) A dielectric slab is slowly inserted inside a parallel plate capacitor connected across a battery to completely fill the space between plates. (S) Total electric energy stored inside capacitor decreases in the process. (T) Electric field in the region decreases.

TestHub · Accepted Answer

(I) Isolated, plates pulled apart: Q is fixed, C falls, so $U = \frac{Q ^{2}}{2 C}$ rises (P); $E = \frac{σ}{ϵ _{0}}$ stays the same (R) and the force $\frac{Q ^{2}}{2 ϵ _{0} A}$ is unchanged (Q).

(II) Dielectric inserted in an isolated capacitor: U falls (S), the force is unchanged (Q) and the field falls by factor k (T).

(III) Battery connected, plates pulled apart: V fixed, C falls, so $U = \frac{1}{2} C V^{2}$ falls (S) and $E = \frac{V}{d}$ falls (T).

(IV) Dielectric inserted with battery connected: C rises so U rises (P); $E = \frac{V}{d}$ is unchanged (R).

I → P,Q,R; II → Q,S,T; III → S,T; IV → P,R - option (A).

Physics - Capacitor Question with Solution | TestHub

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Doubts & Discussion

List - I	List - II
(I) Plates of an isolated, charged, parallel plate, air core capacitor are slowly pulled apart.	(P) Electric energy stored inside capacitor increases in the process.
(II) A dielectric is slowly inserted inside an isolated and charged parallel plate air cored capacitor to completely fill the space between plates.	(Q) Force between the two plates of the capacitor remain unchanged.
(III) Plates of a parallel plate capacitor connected across a battery are slowly pulled apart.	(R) Electric field in the region between plates remain unchanged.
(IV) A dielectric slab is slowly inserted inside a parallel plate capacitor connected across a battery to completely fill the space between plates.	(S) Total electric energy stored inside capacitor decreases in the process.
	(T) Electric field in the region decreases.