CBSE Class 12 Physics Electrostatics Worksheet

Electrostatic MCQ Questions with Answers Class 12 Physics 

Q.- A point charge + Q is placed at the centroid of an equilateral triangle .When second charge +Q is placed at the vertex of the triangle the magnitude of the electrostatic force on the central charge is 8N.The magnitude of the net force on the central charge when a third charge +Q is placed at another vertex of the triangle is

Electrostatic MCQ Questions with Answers Class 12 Physics 

Question. Three charges 2 q, – q and – q are located at the vertices of an equilateral triangle. At the centre of the triangle
(a) the field is zero but potential is non-zero
(b) the field is non-zero, but potential is zero
(c) both field and potential are zero
(d) both field and potential are non-zero

Answer: B

Question. The electric potential due to a small electric dipole at a large distance r from the centre of the dipole is proportional to
(a) r
(b) 1/r
(c) 1/r²
(d) 1/r3

Answer: C

Question. An electron of mass m and charge e is accelerated from rest through a potential difference V in vacuum. Its final speed will be
(a) √2eV/m
(b) √eV/m
(c) e V/2m
(d) e V/m

Answer: A

Question. A positive point charge q is carried from a point B to a point A in the electric field of a point charge + Q at O. If the permitivity of free space is ε₀, the work done in the process is given by 
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Answer: B

Question. Force between two plates of a capacitor is
(a) Q/ε0A
(b) Q²/2ε₀A
(c) Q²/ε₀A
(d) None of these

Answer: B

Question. An alpha particle is accelerated through a potential difference of 106 volt. Its kinetic energy will be
(a) 1 MeV
(b) 2 MeV
(c) 4 MeV
(d) 8 MeV

Answer: B

Question. Two capacitors of capacitances C₁ and C₂ are connected in parallel across a battery. If Q₁ and Q₂ respectively be the charges on the capacitors, then Q₁/Q₂ will be equal to
(a) C₂/C₁
(b) C₁/C₂
(c) C₁²/C₂²
(d) C₂²/C₁2

Answer: B

Question. A system of two parallel plates, each of area A, are separated by distances d₁ and d₂. The space between them is filled with dielectrics of permittivities ε₁ and ε₂. The permittivity of free space is ε₀. The equivalent capacitance of the system is
(a) ε₁ε₂A/ε₂d₁ + ε₁d₂
(b) ε₁ε₂A/ε₁d₁ + ε₂d₂
(c) ε₀A/ε₁d₁ + ε₂d₂
(d) ε₀A/ε₁d₂ + ε₂d₁

Answer: A

Question. Two capacitors C₁ and C₂ in a circuit are joined as shown in figure. The potentials of points A and B are V₁ and V₂ respectively; then the potential of point D will be 
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Answer: C

Question. The capacity of a parallel plate condenser is 10 μF, when the distance between its plates is 8 cm. If the distance between the plates is reduced to 4 cm, then the capacity of this parallel plate condenser will be
(a) 5 μF
(b) 10 μF
(c) 20 μF
(d) 40 μF

Answer: C

Question. A conductor carries a certain charge. When it is connected to another uncharged conductor of finite capacity, then the energy of the combined system is
(a) more than that of the first conductor
(b) less than that of the first conductor
(c) equal to that of the first conductor
(d) uncertain

Answer: B

Question. The magnitude of the electric field E in the annular region of a charged cylindrical capacitor
(a) is same throughout
(b) is higher near the outer cylinder than near the inner cylinder
(c) varies as 1/r, where r is the distance from the axis
(d) varies as 1/r² where r is the distance from the axis

Answer: C

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) √2C
(b) 2 C
(c) C/√2
(d) C/2

Answer: D

Question. A parallel plate capacitor is charged to a certain voltage.
Now, if the dielectric material (with dielectric constant k) is removed then the
(a) capacitance increases by a factor of k
(b) electric field reduces by a factor k
(c) voltage across the capacitor decreases by a factor k
(d) None of these

Answer: D

Question. Two parallel metal plates having charges + Q and – Q face each other at a certain distance between them. If the plates are now dipped in kerosene oil tank, the electric field between the plates will
(a) remain same
(b) become zero
(c) increases
(d) decrease

Answer: D

Question. A parallel plate condenser has a uniform electric field E(V/ m) in the space between the plates. If the distance between the plates is d(m) and area of each plate is A(m²) the energy (joules) stored in the condenser is
(a) E²Ad/∈₀
(b) 1/2 ∈₀ E²
(c) ∈₀ EAd
(d) 1/2 ∈₀ E² Ad

Answer: D

Question. Which of the following figure shows the correct equipotential surfaces of a system of two positive charges? 
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Answer: C

Question. The positive terminal of 12 V battery is connected to the ground. Then the negative terminal will be at
(a) – 6 V
(b) + 12 V
(c) zero
(d) – 12 V

Answer: D

Question. A battery is used to charge a parallel plate capacitor till the potential difference between the plates becomes equal to the electromotive force of the battery. The ratio of the energy stored in the capacitor and the work done by the battery will be
(a) 1/2
(b) 1
(c) 2
(d) 1/4

Answer: A

Question. Four point charges q, q, q and – 3q are placed at the vertices of a regular tetrahedron of side L. The work done by electric force in taking all the charges to the centre of the tetrahedron is (where k = 1/4πε₀)
(a) 6kq²/L
(b) -6kq²/L
(c) 12kq²/L
(d) zero

Answer: B

Question. A hollow metal sphere of radius 5 cm is charged such that the potential on its surface is 10 V. The potential at a distance of 2 cm from the centre of the sphere is
(a) zero
(b) 10 V
(c) 4 V
(d) 10/3 V

Answer: B

Question. Find the dipole moment of a system where the potential 2.0 × 10^–5 V at a point P, 0.1m from the dipole is 3.0 × 10⁴. (Use q = 30°).
(a) 2.57 × 10^–17 Cm
(b) 1.285 × 10^–15 Cm
(c) 1.285 × 10^–17 Cm
(d) 2.57 × 10^–15 Cm

Answer: A

Question. A battery of e.m.f. V volt, resistors R₁ and R₂, a condenser C and switches S₁ and S₂ are connected in a circuit shown. The condenser will get fully charged to V volt when
​
(a) S₁ and S₂ are both closed
(b) S₁ and S₂ are both open
(c) S₁ is open and S₂ is closed
(d) S₁ is closed and S₂ is open

Answer: D

Question. The electric potential at the surface of an atomic nucleus (Z = 50) of radius of 9 × 10^–15 m is
(a) 80 V
(b) 8 × 10⁶ V
(c) 9 V
(d) 9 × 10⁵ V

Answer: B

Question. Three point charges +q , + 2q and – 4q where q = 0.1 mC, are placed at the vertices of an equilateral triangle of side 10 cm as shown in figure. The potential energy of the system is
(a) 3 × 10^–3 J
(b) –3 × 10^–3 J
(c) 9 × 10^–3 J
(d) –9 × 10–3 J

Answer: D