# MCQs for Physics Class 12 with Answers Chapter 1 Electric Charges and Fields

Students of class 12 Physics should refer to MCQ Questions Class 12 Physics Electric Charges and Fields with answers provided here which is an important chapter in Class 12 Physics NCERT textbook. These MCQ for Class 12 Physics with Answers have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 12 Physics. The following MCQs can help you to practice and get better marks in the upcoming class 12 Physics examination

## Chapter 1 Electric Charges and Fields MCQ with Answers Class 12 Physics

MCQ Questions Class 12 Physics Electric Charges and Fields provided below have been prepared by expert teachers of grade 12. These objective questions with solutions are expected to come in the upcoming Standard 12 examinations. Learn the below provided MCQ questions to get better marks in examinations.

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

Ans

D

Question. A body can be negatively charged by
(a) giving excess of electrons to it
(b) removing some electron from it
(c) giving some protons to it
(d) removing some neutrons from it.

Ans

A

Question. How many electrons must be removed from an electrically neutral metal plate to give it a positive charge of 1 × 10–7 coulomb?
(a) 6.25 × 1011
(b) 6.45 × 1013
(c) 6.25 × 10–11
(d) 6.45 × 10–13

Ans

A

Question. When air is replaced by a medium of dielectric constant K, the force of attraction between two charges separated by a distance r
(a) decreases K times
(b) remains unchanged
(c) increases K times
(d) increases K–2 times

Ans

A

Question. A hemisphere is uniformly 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 toawards the diameter
(d) at an angle tilted away from the diameter

Ans

A

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.

Ans

A

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

Ans

A

Question. The unit of permittivity of free space (e0) is
(a) CN–1m–1
(b) Nm2C–2
(c) C2 N–1m–2
(d) C2 N–2m–2

Ans

C

Question. Which of the following is not a property of field lines?
(a) Field lines are continuous curves without any breaks
(b) Two field lines cannot cross each other
(c) Field lines start at positive charges and end at negative charges
(d) They form closed loops

Ans

D

Question. A method for charging a conductor without bringing a charged object in contact with it is called
(a) electrification
(b) magnetisation
(c) electromagnetic induction
(d) electrostatic induction

Ans

D

Question. Two point charges A and B, having charges +q and –q respectively, are placed at certain distance apart and force acting between them is F. If 25% charge of A is transferred to B, then force between the charges becomes:
(a) F
(b) 9F/16
(c) 16F/3
(d) 4F/3

Ans

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.

Ans

C

Question. Two point charges q1 and q2 are at separation r. The force acting between them is given by The constant K depends upon
(a) only on the system of units
(b) only on medium between charges
(c) both on (a) and (b)
(d) neither on (a) nor on (b)

Ans

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.

Ans

A

Question. When the distance between two charged particles is halved, the Coulomb force between them becomes
(a) one-half
(b) one-fourth
(c) double
(d) four times.

Ans

D

Question. What is the angle between the electric dipole moment and the electric field due to it on the axial line?
(a) 0º
(b) 90º
(c) 180º
(d) None of these

Ans

A

Question. In a region of space having a uniform electric field E, a hemispherical bowl of radius r is placed. The electric flux f through the bowl is
(a) 2πRE
(b) 4πR2E
(c) 2πR2E
(d) πR2E

Question. What is the angle between the electric dipole moment and the electric field due to it on the axial line?
(a) 0º
(b) 90º
(c) 180º
(d) None of these

Ans

A

Question. In a region of space having a uniform electric field E, a hemispherical bowl of radius r is placed. The electric flux f through the bowl is
(a) 2πRE
(b) 4πR2E
(c) 2πR2E
(d) πR2E

Ans

C

Question. Gauss’s law is valid for
(a) Any closed surface
(b) Only regular closed surfaces
(c) Any open surface
(d) Only irregular open surfaces.

Ans

A

Question. The spatial distribution of the electric field due to two charges (A, B) is shown in figure. Which one of the following statements is correct?

(a) A is + ve and B is – ve and |A|>|B|
(b) A is – ve and B is + ve, |A|=|B|
(c) Both are + ve but A>B
(d) Both are – ve but A>B

Ans

A

Question. Two charges are at distance d apart in air. Coulomb force between them is F. If a dielectric
material of dielectric constant K is placed between them, the Coulomb force now becomes
(a) F/K
(b) FK
(c) F/K2
(d) K2F

Ans

A

Question. There are two kinds of charges—positive charge and negative charge. The property which differentiates the two kinds of charges is called
(a) amount of charge
(b) polarity of charge
(c) strength of charge
(d) field of charge

Ans

B

Question. A cup contains 250 g of water. The number of negative charges present in the cup of water is
(a) 1.34 × 107 C
(b) 1.34 × 1019 C
(c) 3.34 × 107 C
(d) 1.34 × 10–19 C

Ans

A

Question. Three charges +4q, Q and q are placed in a straight line of length l at points at distance 0, l/2, and l respectively. What should be Q in order to make the net force on q to be zero?
(a) –q
(b) –2q
(c) – (q/2)
(d) 4q

Ans

A

Question. The electric field strength at a distance r from a charge q is E. What will be electric field strength if the distance of the observation point is increased to 2 r?
(a) E/2
(b) E/4
(c) E/6
(d) None of these

Ans

B

Question. The surface density on the copper sphere is s. The electric field strength on the surface of the sphere is
(a) s
(b) s/2
(c) Q / 2eo
(d) Q / eo

Question. The electric field strength at a distance r from a charge q is E. What will be electric field strength if the distance of the observation point is increased to 2 r?
(a) E/2
(b) E/4
(c) E/6
(d) None of these

Ans

B

Question. The surface density on the copper sphere is s. The electric field strength on the surface of the sphere is
(a) s
(b) s/2
(c) Q / 2eo
(d) Q / eo

Ans

D

Question. The electric field due to a uniformly charged sphere of radius R as a function of the distance from its centre is represented graphically by

Ans

B

Question. If y E.dS = 0 over a surface, then
(a) the electric field inside the surface and on it is zero.
(b) the electric field inside the surface is necessarily uniform.
(c) the number of flux lines entering the surface must be equal to the number of flux lines  leaving it.
(d) all charges must necessarily be outside the surface.

Ans

C

Question. Which among the curves shown in figure possibly represent electrostatic field lines?

Ans

B

7. At the centre of a cubical box + Q charge is placed. The value of total flux that is coming out a wall is
(a) Q / eo
(b) Q / 3eo
(c) Q / 4eo
(d) Q / 6eo

Ans

D

Question. An electron falls from the rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is
(a) smaller
(b) 5 times bigger
(c) 10 times bigger
(d) equal

Ans

A

Question. A cylinder of radius R and length l is placed in a uniform electric field E parallel to the axis of the cylinder. The total flux over the curved surface of the cylinder is
(a) zero
(b) πR2E
(c) 2πR2E
(d) E / πR2

Ans

A

Question. An electric dipole when placed in a uniform electric field E will have minimum potential energy if the dipole moment makes the following angle with E.
(a) π
(b) π/2
(c) zero
(d) 3 π/2

Ans

C

Question. If a charge is moved against the coulomb force of an electric field, then
(a) work is done by the electric field
(b) energy is used from some outside source
(c) the strength of the field is decreased
(d) the energy of the system is decreased

Ans

B

Question. In a medium of dielectric constant K, the electric field is Ē  If Î0 is permittivity of the free space, the electric displacement vector is

Ans

D

Question. The charge given to any conductor resides on its outer surface, because
(a) the free charge tends to be in its minimum potential energy state
(b) the free charge tends to be in its minimum kinetic energy state
(c) the free charge tends to be in its maximum potential energy state.
(d) the free charge tends to be in its maximum kinetic energy state

Ans

A

Question. Two conducting spheres of radii r1 and r2 are charged to the same surface charge density. The ratio of electric fields near their surface is
(a) r12 / r22
(b) r22 / r12
(c) r1 / r2
(d) 1 : 1

Ans

D

Question. What is the value of E in the space outside the sheets?
(a) s/eo
(b) s/2eo
(c) E ¹ 0
(d) 2s/eo

Ans

C

Question. A charge q is placed at the centre of the open end of a cylindrical vessel. The flux of the electric field through the surface of the vessel is

(a) zero
(b) q/eo
(c) q/2eo
(d) 2q/eo

Ans

A

Question. Identify the wrong statement in the following. Coulomb’s law correctly describes the electric force that
(a) binds the electrons of an atom to its nucleus
(b) binds the protons and neutrons in the nucleus of an atom
(c) binds atoms together to form molecules
(d) binds atoms and molecules together to form solids

Ans

B

Question. Two thin infinite parallel sheets have uniform surface densities of charge + s and – s. Electric field in the space between the two sheets is
(a) s/eo
(b) s/2eo
(c) 2s/eo
(d) zero

Ans

A

Question. A charge Q is enclosed by a Gaussian spherical surface of radius R. If the radius is doubled, then the outward electric flux will
(a) increase four times
(b) be reduced to half
(c) remain the same
(d) be doubled

Ans

C

Question. Two charges are at a distance d apart. If a copper plate of thickness d/2 is kept between them, the effective force will be
(a) F/2
(b) zero
(c) 2F
(d) 2 F

Ans

B

Question. The insulation property of air breaks down when the electric field is 3 × 106 Vm–1. The maximum charge that can be given to a sphere of diameter 5 m is approximately
(a) 2 × 10–2 C
(b) 2 × 10–3 C
(c) 2 × 10–4 C
(d) 2 × 10–5 C

Ans

B

Question. The E-r curve for an infinite linear charge distribution will be

Ans

C

Question. When air is replaced by a dielectric medium of force constant K, the maximum force of attraction between two charges, separated by a distance
(a) decreases K-times
(b) increases K-times
(c) remains unchanged
(d) becomes 1/K2 times

Ans

A

Question. A point Q lies on the perpendicular bisector of an electrical dipole of dipole moment p. If the distance of Q from the dipole is r (much larger than the size of the dipole), then the electric field at Q is proportional to
(a) p–1 and r–2
(b) p and r–2
(c) p2 and r–3
(d) p and r–3

Ans

D

Question. A particle of mass m and charge q is placed at rest in a uniform electric field E and then released. The kinetic energy attained by the particle after moving a distance y is
(a) q E y2
(b) q E2 y
(c) q E y
(d) q2 E y

Ans

C

Question. Intensity of an electric field (E) depends on distance r, due to a dipole, is related as
(a) E ∝ (1/r)
(b) E ∝ (1/r2)
(c) E ∝ (1/r4)
(d) E ∝ (1/r4)

Ans

C

Question. The formation of a dipole is due to two equal and dissimilar point charges placed at a
(a) short distance
(b) long distance
(c) above each other
(d) none of these

Ans

A

Question. The electric field intensity just sufficient to balance the earth’s gravitational attraction on an electron will be: (given mass and charge of an electron respectively are 9.1´10-31kg and 1.6´10-19C.)
(a) –5.6 × 10–11 N/C
(b) –4.8 × 10–15 N / C
(c) –1.6 × 10–19 N/C
(d) –3.2 × 10–19 N / C

Ans

A

#### Fill in the Blanks

Question. Two point charges are separated by some distance inside vacuum. When space between the charges is filled by some dielectric, the force between two point charges _______________.

decreases

Question. The quantisation of charge was experimentally demonstrated by _______________ in 1912.

Millikan

Question. A simple apparatus to detect charge on a body is the _______________.

gold-leaf electroscope

Question. Two point charges, one coulomb each are separated by vacuum and placed I meter apart from each other. The force acting between them is _______________.

9 × 109 N

Question. A proton at rest has a charge e. When it moves with high speed v, its charge is _______________.

e

Question. The concept of field was first introduced by _______________ and is now among the central concepts in physics.

Question. Direction of electric field intensity due to a dipole on equatorial point is _______________ to the direction of dipole moment.

opposite

Question. The value of the permittivity of free space (e0) in SI unit is _______________.

8.854 × 10–12 C2N–1m–2

Question. The process of sharing the charges with the earth is called _______________.

grounding or earthing

Question. Two equal and opposite charges of magnitude 0.2 × 10–6 C are 15 cm apart, the magnitude and direction of the resultant electric intensity E at a point midway between the charge is ___________.