CBSE Class 12 Physics Electrostatic Potential And Capacitance Worksheet

Important Questions for NCERT Class 12 Physics Electrostatic Potential And Capacitance

Question. A capacitor is charged by using a battery which is then disconnected. A dielectric slab is introduced between the plates which results in

(a) increase in the potential difference across the plates and reduction in stored energy but no change in the charge on the plates
(b) decrease in the potential difference across the plates and reduction in the stored energy but no change in the charge on the plates
(c) reduction of charge on the plates and increase of potential difference across the plates
(d) increase in stored energy but no change in potential difference across the plates

Question. A capacitor is charged with a battery and energy stored is U. After disconnecting battery another capacitor of same capacity is connected in parallel to the first capacitor. Then energy stored in each capacitor is   
(a) U/2
(b) U/4
(c) 4U
(d) 2U 

Question. Minimum numbers of 8mF and 250 V capacitors are used to make a combination of 16mF and 1000V are: 
(a) 4
(b) 32
(c) 8
(d) 3

Question. A bullet of mass 2 g is having a charge of 2 mC. Through what potential difference must it be accelerated, starting from rest, to acquire a speed of 10 m/s ? 
(a) 5 kV
(b) 50 kV
(c) 5 V
(d) 50 V

Question. The electric potential at a point in free space due to charge Q coulomb is Q × 1011 volts. The electric field at that point is   C
(a) 4pe0Q × 1020 volt/m
(b) 12pe0Q × 1022 volt/m
(c) 4pe0Q × 1022 volt/m
(d) 12pe0Q × 1020 volt/m 

Question. A short electric dipole has a dipole moment of 16 × 10^–9 C m. The electric potential due to the dipole at a point at a distance of 0.6 m from the centre of the dipole, situated on a line making an angle of 60° with the dipole axis is (1/4πε0 = 9x10⁹ Nm²/C² )   
(a) 50 V
(b) 200 V
(c) 400 V
(d) zero 

Question. Two metal spheres, one of radius R and the other of radius 2R respectively have the same surface charge density s. They are brought in contact and separated.   
What will be the new surface charge densities on them?
(a) σ1 = 5/6σ ,σ2 =5/2σ
(b) σ1 = 5/2σ ,σ2 =5/6σ
(c) σ1 = 5/2σ ,σ2 =5/3σ
(d) σ1 = 5/3σ ,σ2 =5/6σ

Question. An insulated charged sphere of radius 5 cm has a potential of 10 V at the surface. The potential at the centre will be 
(a) same as that at 5 cm from the surface
(b) same as that at 25 cm from the surface
(c) 10 V
(d) zero

Question. If potential (in volts) in a region is expressed as V(x, y, z) = 6xy – y + 2yz, the electric field (in N/C) at point (1, 1, 0) is   
(a) -(2î +3j + k)
(b) -(6i + 9j+k)
(c) -(3i+5j+3k)
(d) −(6i + 5j+2k)

Question. 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) decreases by a factor of 2
(b) remains the same
(c) increases by a factor of 2
(d) increases by a factor of 4. 

Question. 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 change in energy stored is 1/2CV²(1/K-1).
(b) The charge on the capacitor is not conserved.
(c) The potential difference between the plates decreases K times.
(d) The energy stored in the capacitor decreases K times. 

Question. A parallel plate capacitor has a uniform electric field E in the space between the plates. If the distance between the plates is d and area of each plate is A, the energy stored in the capacitor is   
(a) 1/2 ε₀ E²
(b) E²Ad /ε₀
(c) 1/2 ε₀ E²Ad
 (d) ε₀EAd

Important Questions for NCERT Class 12 Physics Electrostatic Potential And Capacitance

Question. In a region, the potential is represented by V(x, y, z) = 6x – 8xy – 8y + 6yz, where V is in volts and x, y, z are in metres. The electric force experienced by a charge of 2 coulomb situated at point (1, 1, 1) is   
(a) 6 5N
(b) 30 N
(c) 24 N
(d) 4 √35N

Question. The electric potential V at any point (x, y, z), all in metres in space is given by V = 4x2 volt. The electric field at the point (1, 0, 2) in volt/meter, is   
(a) 8 along negative X-axis
(b) 8 along positive X-axis
(c) 16 along negative X-axis
(d) 16 along positive X-axis

Question. A 40 μF capacitor in a defibrillator is charged to 3000 V. The energy stored in the capacitor is set through the patient during a pulse of duration 2 ms. The power delivered to the patient is :
(a) 45 kW
(b) 90 kW
(c) 180 kW
(d) 360 kW

Answer  B

Question. Identical charges (–q) are placed at each corners of cube of side b, then electrostatic potential energy of charge (+q) which is placed at centre of cube will be   
(a) −4√2 q² /πε₀b
(b) −8√2 q² /πε₀b
(c) −4q² /√3πε₀b
(d) −8√2 q² /4πε₀b

Question. In bringing an electron towards another electron, the electrostatic potential energy of the system   
(a) becomes zero
(b) increases
(c) decreases
(d) remains same

Question. Two metallic spheres of radii 1 cm and 3 cm are given charges of –1 × 10^–2 C and 5 × 10^–2 C, respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is   
(a) 2 × 10^–2 C
(b) 3 × 10^–2 C
(c) 4 × 10^–2 C
(d) 1 × 10^–2 C 

Question. A parallel plate air capacitor has a capacitance C. When it is half filled with a dielectric of dielectric constant 5, the percentage increase in the capacitance will be 
(a) 400%
(b) 66.6%
(c) 33.3%
(d) 200%

Answer  B

Question. An electric dipole of moment p is placed in an electric field of intensity E. The dipole acquires a position such that the axis of the dipole makes an angle q with the direction of the field. Assuming that the potential energy of the dipole to be zero when q = 90°, the torque and the potential energy of the dipole will respectively be   
(a) pEsinq, –pEcosq
(b) pEsinq, –2pEcosq
(c) pEsinq, 2pEcosq
(d) pEcosq, –pEsinq 

Question. An electric dipole of moment ^→p is lying along a uniform electric field ^→E. The work done in rotating the dipole by 90° is 
(a) pE
(b) 2pE
(c) pE/2
(d) 2pE 

Question. An electric dipole has the magnitude of its charge as q and its dipole moment is p. It is placed in a uniform electric field E. If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively   
(a) 2q · E and minimum 
(b) q · E and p · E
(c) zero and minimum
(d) q · E and maximum

Question. There is an electric field E in x-direction. If the work done on moving a charge of 0.2 C through a distance of 2 m along a line making an angle 60° with x-axis is 4 J, then what is the value of E ?   
(a) 5 N/C
(b) 20 N/C
(c) 3 N/C
(d) 4 N/C 

Question. An electric dipole of moment p is placed in the position of stable equilibrium in uniform electric field of intensity E. This is rotated through an angle q from the initial position. The potential energy of the electric dipole in the final position is   
(a) –pE cosq
(b) pE(1 – cosq)
(c) pE cosq
(d) pE sinq

Important Questions for NCERT Class 12 Physics Electrostatic Potential And Capacitance

Question. A parallel plate condenser with oil between the plates (dielectric constant of oil K = 2) has a capacitance C. If the oil is removed, then capacitance of the capacitor becomes   
(a) C/√2
(b) 2C
(c) 2C
(d) C/2

Question. A condenser of capacitor 50mF is charged to 10 volt, the energy stored is : 
(a) 5´10-3 J
(b) 2.5´10-3 J
(c) 3.75´10-3 J
(d) 1.25´10-3 J

Question. Some charge is being given to a conductor. Then its potential is   
(a) maximum at surface
(b) maximum at centre
(c) remain same throughout the conductor
(d) maximum somewhere between surface and centre.

Question. Two metallic spheres of radii 1 cm and 2 cm are given charges 10^–2 C and 5 × 10^–2 C respectively.
If they are connected by a conducting wire, the final charge on the smaller sphere is   
(a) 3 × 10^–2 C
(b) 4 × 10^–2 C
(c) 1 × 10^–2 C
(d) 2 × 10^–2 C

Question. Equipotential surfaces associated with an electric field which is increasing in magnitude along the x-direction are : 
(a) planes parallel to yz-plane
(b) planes parallel to xy-plane
(c) planes parallel to xz -plane
(d) coaxial cylinders of increasing radii around the x-axis

Question. 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) CV²/d
(b) C²V²/2d²
(c) C²V²/d
(d) CV²/d

Question. A parallel plate air capacitor is charged to a potential difference of V volts. After disconnecting the charging battery the distance between the plates of the capacitor is increased using an insulating handle. As a result the potential difference between the plates   
(a) increases
(b) decreases
(c) does not change
(d) becomes zero

Question. The capacitance of a parallel plate capacitor with air as medium is 6 mF. With the introduction of a dielectric medium, the capacitance becomes 30 mF. The permittivity of the medium is (e0 = 8.85 × 10^–12 C2 N^–1 m^–2)   
(a) 0.44 × 10^–13 C² N^–1 m^–2
(b) 1.77 × 10^–12 C² N^–1 m^–2
(c) 0.44 × 10^–10 C² N^–1 m^–2
(d) 5.00  C² N^–1 m^–2

Question. The maximum electric field that can be held in air without producing ionisation of air is 107 V/m.
The maximum potential therefore, to which a conducting sphere of radius 0.10 m can be charged in air is 
(a) 109 V
(b) 108 V
(c) 107 V
(d) 106 V

Question. A hollow metallic sphere of radius 10 cm is charged such that potential of its surface is 80 V. The potential at the centre of the sphere would be 
(a) 80 V
(b) 800 V
(c) zero
(d) 8 V

Question. Two charges of magnitude + q and – 3q are placed 100 cm apart. The distance from + q between the charges where the electrostatic potential is zero is : 
(a) 25 cm
(b) 50 cm
(c) 75 cm
(d) 80 cm

Question. Three capacitors each of capacity 4 mF are to be connected in such a way that the effective capacitance is 6 mF. This can be done by   
(a) connecting all of them in series
(b) connecting them in parallel
(c) connecting two in series and one in parallel
(d) connecting two in parallel and one in series.