CBSE Class 12 Physics Electric Charges And Fields Worksheet Set 05

Question. A charge +q is at a distance L/2 above a square of side L. Then what is the flux linked with the surface?
(a) 9/4ε₀
(b) 2q/3ε₀
(c) q/6ε₀
(d) 6q/ε₀

Answer: C

Question. Positive and negative point charges of equal magnitude are kept at (0,0,a/2) and (0,0,-a/2) respectively. The work done by the electric field when another positive point charge is moved from (–a, 0, 0) to (0, a, 0) is
(a) positive
(b) negative
(c) zero
(d) depends on the path connecting the initial and final positions

Answer: C

Question. A charge ‘q’ is placed at the centre of the line joining two equal charges ‘Q’. The system of the three charges will be in equilibrium if ‘q’ is equal to
(a) Q/2
(b) – Q/4
(c) Q/4
(d) – Q/2

Answer: B

Question. An electric dipole of dipole moment p is aligned parallel to a uniform electric field E. The energy required to rotate the dipole by 90° is 
(a) pE²
(b) p²E
(c) pE
(d) infinity

Answer: C

Question. Two positive ions, each carrying a charge q, are separated by a distance d. If F is the force of repulsion between the ions, the number of electrons missing from each ion will be (e being the charge of an electron) 

Answer: C

Question. The electric dipole is situated is an electric field as shown in fig 1. The dipole and electric field are both in the plane of the paper. The dipole is rotated about an axis perpendicular to plane of paper passing through A in anticlockwise direction. If the angle of rotation (θ) is measured with respect to the direction of electric field, then the torque (𝜏) experienced by the dipole for different values of the angle of rotation θ will be represented in fig. 2, by 

(a) curve (1)
(b) curve (2)
(c) curve (3)
(d) curve (4)

Answer: B

Question. Three charges, each +q, are placed at the corners of an isosceles triangle ABC of sides BC and AC, 2a. D and E are the mid points of BC and CA. The work done in taking a charge Q from D to E is
(a) 3qQ/8πε₀a
(b) qQ/4πε₀a
(c) zero
(d) 3qQ/4πε₀a

Answer: C

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

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 θ with the direction of the field. Assuming that the potential energy of the dipole to be zero when = 90°, the torque and the potential energy of the dipole will respectively be
(a) p E sin θ, – p E cos θ
(b) p E sin θ, –2 p E cos θ
(c) p E sin θ, 2 p E cos θ
(d) p E cos θ, – p E cos θ

Answer: A

Question. If a charge q is placed at the centre of the line joining two equal charges Q such that the system is in equilibrium then the value of q is
(a) Q/2
(b) –Q/2
(c) Q/4
(d) –Q/4

Answer: D

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

Answer: D

Question. Among two discs A and B, first have radius 10 cm and charge 10^–6 μC and second have radius 30 cm and charge 10^–5μC.
When they are touched, charge on both q_A and q_B respectively will, be
(a) q_A = 2.75μC, q_B=3.15μC
(b) q_A = 1.09μC, q_B = 1.53μC
(c) q_A = q_B = 5.5μC
(d) None of these

Answer: C

Question. The electric intensity due to a dipole of length 10 cm and having a charge of 50⁰ μC, at a point on the axis at a distance 20 cm from one of the charges in air, is
(a) 6.25 × 10⁷ N/C
(b) 9.28 × 10⁷ N/C
(c) 13.1 × 10¹¹ N/C
(d) 20.5 × 10⁷ N/C

Answer: A

Question. The electric flux through the surface 

(a) in Fig. (iv) is the largest
(b) in Fig. (iii) is the least
(c) in Fig. (ii) is same as Fig. (iii) but is smaller than Fig. (iv)
(d) is the same for all the figures

Answer: D

Question. Five charges q₁, q₂, q₃,q₄, and q₅ are fixed at their positions as shown in Figure, S is a Gaussian surface. The Gauss’ law is given by 

Which of the following statements is correct?

(a) E on the LHS of the above equation will have a contribution from q₁, q₅ and q₁, q₅ and q₃ while q on the RHS will have a contribution from q₂ and q4 only
(b) E on the LHS of the above equation will have a contribution from all charges while q on the RHS will have a contribution from q₂ and q4 only
(c) E on the LHS of the above equation will have a contribution from all charges while q on the RHS will have a contribution from q₁, q₃ and q₅.
(d) Both E on the LHS and q on the RHS will have contributions from q₂ and q₄ only

Answer: B

Question. Figure shows electric field lines in which an electric dipole P is placed as shown. Which of the following statements is correct?
(a) The dipole will not experience any force
(b) The dipole will experience a force towards right
(c) The dipole will experience a force towards left
(d) The dipole will experience a force upwards

Answer: C

Question. A point charge + q is placed at a distance d from an isolated conducting plane. The field at a point P on the other side of the plane is
(a) directed perpendicular to the plane and away from the plane
(b) directed perpendicular to the plane but towards the plane
(c) directed radially away from the point charge
(d) directed radially towards the point charge.

Answer: A

Question. A hemisphere is uniformely charged positively. The electric field at a point on a diameter away from the centre is directed
(a) perpendicular to the diameter
(b) parallel to the diameter
(c) at an angle tilted towards the diameter
(d) at an angle tilted away from the diameter

Answer: A

Question. Three charge q, Q and 4q are placed in a straight line of length l at points distant 0, 1/2 and l respectively from one end. In order to make the net froce on q zero, the charge Q must be equal to
(a) –q
(b) – 2q
(c) -q/2
(d) q

Answer: A

Question. A solid conducting sphere of radius a has a net positive charge 2Q. A conducting spherical shell of inner radius b and outer radius c is concentric with the solid sphere and has a net charge – Q. The surface charge density on the inner and outer surfaces of the spherical shell will be 

Answer: A

Question. In figure two positive charges q₂ and q₃ fixed along the yaxis, exert a net electric force in the + x-direction on a charge q1 fixed along the x-axis. If a positive charge Q is added at (x, 0), the force on q₁
(a) shall increase along the positive x-axis
(b) shall decrease along the positive x-axis
(c) shall point along the negative x-axis
(d) shall increase but the direction changes because of the intersection of Q with q₂ and q₃

Answer: A

Question. A point positive charge is brought near an isolated conducting sphere (figure). The electric field is best given by 

Answer: A

Question. A square surface of side L meter in the plane of the paper is placed in a uniform electric field E (volt/m) acting along the same plane at an angle θ with the horizontal side of the square as shown in Figure. The electric flux linked to the surface, in units of volt. m, is
(a) EL²
(b) EL² cos θ
(c) EL² sin θ
(d) zero

Answer: D

Question. Two pith balls carrying equal charges are suspended from a common point by strings of equal length. The equilibrium separation between them is r. Now the strings are rigidly clamped at half the height. The equilibrium separation between the balls now become 

Answer: A

DIRECTIONS : Each question contains
STATEMENT-1 and STATEMENT-2. Choose the correct answer from the following-
(a) Statement-1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1
(b) Statement-1 is true, Statement-2 is true; Statement -2 is NOT a correct explanation for Statement-1
(c) Statement-1 is true, Statement-2 is false
(d) Statement-1 is false, Statement-2 is true

Question. Statement-1 : The positive charge particle is placed in front of a spherical uncharged conductor. The number of lines of forces terminating on the sphere will be more than those emerging from it.
Statement-2 : The surface charge density at a point on the sphere nearest to the point charge will be negative and maximum in magnitude compared to other points on the sphere.

Answer: D

Question. Statement-1 : When a conductor is placed in an external electrostatic field, the net electric field inside the conductor becomes zero after a small instant of time.
Statement-2 : It is not possible to set up an electric field inside a conduct

Answer: C

Question. Statement-1 : A deuteron and an a-particle are placed in an electric field. If F₁ and F₂ be the forces acting on them and a₁ and a₂ be their accelerations respectively then, a₁ = a₂.
Statement-2 : Forces will be same in electric field.

Answer: C

Question. Statement-1 : Four point charges q₁, q₂, q₃ and q₄ are as shown in figure. The flux over the shown Gaussian surface depends only on charges q₁ and q₂. 

Statement-2 : Electric field at all points on Gaussian surface depends only on charges q₁ and q₂.

Answer: C

Question. Statement-1 : A uniformly charged disc has a pin hole at its centre. The electric field at the centre of the disc is zero.
Statement-2 : Disc can be supposed to be made up of many rings. Also electric field at the centre of uniformly charged ring is zero.

Answer: A

Question. Statement-1 : Consider two identical charges placed distance 2d apart, along x-axis. 

The equilibrium of a positive test charge placed at the point O midway between them is stable for displacements along the x-axis.
Statement-2: Force on test charge is zero.

Answer: B

Please click on below link to download CBSE Class 12 Physics Electric Charges And Fields Worksheet Set B