- Subject:
Physics

- Chapter:
Electrostatic Potential and Capacitance

A capacitor is charged by a battery.The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system

(a)increases by a factor of 4

(b)decreases by a factor of 2

(c)remain the same

(d)increases by a factor of 2

The diagrams below show regions of equipotents.

A positive charge is moved from A to B in each diagram.

(a) Maximum work is requried to move q in figure(iii)

(b) In all the four cases,the work done is the same

(c) Minimum work is requried to move q in the figure(i)

(d) Maximum work is required to move q in figure(ii)

A parallel-plate capacitor of area A, plate separation d and capacitance C is filled with four dielectric materials having dielectric constants ${k}_{1},{k}_{2},{k}_{3}$and ${k}_{4}$ as shown in the figure below. If a single dielectric material is to be used to have the same capacitance C in this capacitor, then its dielectric constant k is given by

(a) $k={k}_{1}+{k}_{2}+{k}_{3}+3{k}_{4}$

(b) $k=\frac{2}{3}\left({k}_{1}+{k}_{2}+{k}_{3}\right)+2{k}_{4}$

(c) $\frac{2}{k}=\frac{3}{{k}_{1}+{k}_{2}+{k}_{3}}+\frac{1}{{k}_{4}}$

(d) $\frac{1}{k}=\frac{1}{{k}_{1}}+\frac{1}{{k}_{2}}+\frac{1}{{k}_{3}}+\frac{3}{2{k}_{4}}$

The potential difference $\left({V}_{A}-{V}_{B}\right)$ between the points A and B in the given figure is

(a) -3V (b) +3V

(c) +6V (d) +9V

A capacitor of 2$\mu F$ is charged as shown in the figure. When the switch S is turned to position 2, the percentage of its stored energy dissipated is

(a) 20% (b) 75%

(c) 80% (d) 0%

A small signal voltage v(t)=V_{o} sinωt is applied across an ideal capacitor C

(a) over a full cycle the capacitor C does not consume any energy from the voltage source

(b) current I(t) is in phase with voltage V(t)

(c) current I(t) leads voltage V(t) by 180°

(d) current I(t) lags voltage V(t) by 90°

A parallel plate air capacitor of capacitance C is connected , to a cell of emf V and then disconnected from it. A dielectric slab of dielectric constant K, which can just fill the air gap of the capacitor, is now inserted in it. Which of the following is incorrect?

(a) The potential difference between the plates decreases K times

(b) The energy stored in the capacitor decreases K times

(c) The change m energy stored is $\frac{1}{2}$CV^{2}($\frac{1}{K}$-1)

(d) The charge on the capacitor is not conserved

A parallel plate air capacitor has capacity C, distance of separation between plates is d and potential difference V is applied between the plates. Force of attraction between the plates of the parallel plate air capacitor is

(a)C^{2}V^{2}/2d

(b)CV^{2}/2d

(c)CV^{2}/d

(d)C^{2}V^{2}/2d^{2}

Two thin dielectric slabs of dielectric constants K_{1}&K_{2} (K_{1},K2) are inserted between plates of a parallel capacitor, as shown in the figure. The variation of electric field E between the plates with distance d as measured from plate P is correctly shown by

(a)(b)(c)(d)

A,B and C are three points in a uniform electric field. The electric potential is

(a) maximum at A

(b) maximum at B

(c) maximum at C

(d) same at all the three points A,B and C