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NCERT Solutions for class 12 Physics | Chapter 2 - Electrostatic Potential Capacitance

(1) If a +ve charge is moved from low to high potential region, the electric potential energy:
[A] decreases
[B] increases
[C] remain the same
[D] may increase or decrease
Answer: increases
(2) Minimum number of capacitor of 2µF each required to obtain a capacitance of 5µF will be:
[A] 4
[B] 3
[C] 5
[D] 6
Answer: 4

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(3) When a dielectric slab is introduced between the plates of a parallel plate capacitor which remains connected to a battery then charge on the plates relative to earlier charge is :
[A] more
[B] less
[C] less or may be more
[D] same
Answer: more
(4) A capacitor is connected to a cell of emf E having some internal resistance r, the potential across the:
[A] cell is < E
[B] cell is E
[C] cell is > E
[D] capacitor is E
Answer: cell is E
(5) Twenty seven drops of mercury are charged simultaneously to the same potential of 10 volts. What will be potential if all the charged drops are made to combine to form one large drop ?
[A] 180 V
[B] 90 V
[C] 120 V
[D] 45 V
Answer: 90 V
(6) Two capacitors of capacitance 6 µF and 4 µF are put in series across a 120 V battery. What is the potential difference across the 4 µF capacitor ?
[A] 72 V
[B] 60 V
[C] 48 V
[D] zero
Answer: 72 V
(7) Which of the following is blocked by a capacitor ?
[A] A.C.
[B] D.C.
[C] Both A.C. and D.C.
[D] Neither A.C. nor D. C
Answer: D.C.
(8) An electron initially at rest is accelerated through a potential difference of one volt. The energy gained by electron is:
[A] 1 J
[B] 1.6 × 10-19 J
[C] 10-19 J
[D] None of these
Answer: 1.6 × 10-19 J
(9) Two conducting spheres of radii r1 and r2 are equally charged. The ratio of their potential is
[A] (r1/r2
[B] (r1r2
[C] (r1/r2)
[D] (r2/r1)
Answer: (r1r2
(10) The capacitance of a capacitor will decrease if we introduce a slab of:
[A] copper
[B] aluminium
[C] zinc
[D] None of these
Answer: None of these
(11) The dimensions of fall of potential per unit distance are given by:
[A] [MLT-3 A-1]
[B] [ML2T-2A-1]
[C] [ML2T-2A-3]
[D] [MLT-2A-2]
Answer: [ML2T-2A-3]
(12) In which of the following forms is the energy stored in a capacitor?
[A] Charge
[B] Potential
[C] Capacitance
[D] Electric field
Answer: Electric field
(13) A bird sitting on a high power line:
[A] gets killed instantly
[B] gets a mild shock
[C] gets a fatal shock
[D] is not affected practically
Answer: is not affected practically
(14) The P.E. of an electric dipole is maximum when it makes an angle θ with electric field. The value of θ is :
[A] π/2
[B] π
[C] zero
[D] 3π/2
Answer: π
(15) The capacitance of earth, viewed as a spherical conductor of radius 6408 km is:
[A] 1420 µF
[B] 712 µF
[C] 680 µF
[D] 540 µF
Answer: 712 µF
(16) Two capacitors of 3 µF and 6 µF are connected in series with a battery of P.d. 12 V. The P.d. across 3µF and 6µF

capacitors respectively will be :

[A] 8 V, 4 V
[B] 6 V, 6 V
[C] 4 V, 8 V
[D] 9 V, 3 V
Answer: 8 V, 4 V
(17) The surface density of charge is measure:
[A] Cm-1
[B] Cm-2
[C] Cm-3
[D] JC-1
Answer: Cm-2
(18) Choose the SI unit of electric potential energy :
[A] Joule
[B] Coulomb
[C] Netwon per coulomb
[D] Erg
Answer: Joule
(19) A dielectric is placed in between the two parallel plates of a capacitor as shown in the figure. The dielectric constant of the dielectric being K. If the initial capacity is C, then the new capacity will be:

[A] (K + l).C
[B] K.C
[C]
[D] (k – l) C
Answer:
(20) A polythene piece rubbed with wool is found to have a negative charge of 6.4 × 10-9c. How many electrons have been transferred during the process?
[A] 4 × 1012
[B] 4 × 1011
[C] 4 × 1010
[D] None of these
Answer: 4 × 1010

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