CBSE 12th Term-1 2021-22 : Physics Important MCQ Questions with Answers

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CBSE 12th Term-1 2021-22 : Physics Important MCQ Questions with Answers

Physics is one of the toughest subjects for students. Preparing for Physics is not an easy task either. Preparing for your Physics paper requires consistency, hard work and some practice. We’re all aware of your difficulties in studying for the boards. This post also includes the solutions to the CBSE Class 12 Term 1 Physics MCQs. Before you go, check out CBSE Class 12 Term 1 Physics Important MCQ Questions With Answers, and best of luck with your CBSE Class 12 Term 1 Physics test!

Q.1 Electric field at a point varies as r° for
(a) an electric dipole
(b) a point charge
(c) a plane infinite sheet of charge
(d) a line charge of infinite length

Answer: (c) a plane infinite sheet of charge

Q.2 A positively charged particle is released from rest in a uniform electric field. The electric potential energy of the charge
(a) remains a constant because the electric field is uniform.
(b) increases because the charge moves along the electric field.
(c) decreases because the charge moves along the electric field.
(d) decreases because the charge moves opposite to the electric field.

Answer: (c) decreases because the charge moves along the electric field.

Q.3 Figures show some equipotential lines distributed in space. A charged object is moved from point A to point B.
(a) The work done in Fig. (i) is the greatest.
(b) The work done in Fig. (ii) is least.
(c) The work done is the same in Fig. (i), Fig.(ii) and Fig. (iii).
(d) The work done in Fig. (iii) is greater than Fig. (ii) but equal to that in Fig. (i).

Answer: (c) The work done is the same in Fig. (i), Fig.(ii) and Fig. (iii).

Q.4 Equipotential at a great distance from a collection of charges whose total sum is not zero are approximately
(a) spheres
(b) planes
(c) paraboloids
(d) ellipsoids

Answer: (a) spheres

Q.5 Two small spheres each carrying a charge q are placed r metre apart. If one of the spheres is taken around the other one in a circular path of radius r, the work done will be equal to
(a) force between them × r
(b) force between them × 2πr
(c) force between them/2πr
(d) zero

Answer: (d) zero

Q.6 The charge flowing in a conductor varies with time as :
q = αt +12 βt² + 16 γt³
Where α, β, γ are positive constants. Then the initial current (l) is given by the condition :
(a) l = α
(b) l = α²
(c) l = α^-1
(d) None of these

Answer: (a) l = α

Q.7 A capacitor has capacitance C and reactance X, if capacitance and frequency become double, then reactance will be
(a) 4X
(b) X/2
(c) X/4
(d) 2X

Answer: (c) X/4

Q.8 Given below are two statements labelled as Assertion (A) and Reason (R)

Assertion : We cannot think of a magnetic field configuration with three poles
Reason : A bar magnet does exert a torque on itself due to its own field.

Select the most appropriate answer from the options given below:

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A.

(d) A is false and R is also false.

Answer: (b) Both A and R are true but R is not the correct explanation of A.

Q.9 The quantisation of charge implies

(a) charge can’t be destroyed

(b) charge exists on particles

(d) charge, which is a fraction of coulomb on a particle

Answer- (d) charge, which is a fraction of coulomb on a particle

Q.10 The unit of electric dipole moment is

(a) newton

(b) coulomb

(d) debye

Answer- (d) debye

Q.11 Charge is the property associated with the matter due to which it produces and experiences

(a) electric effects only

(b) magnetic effects only

(d) None of these

Answer- (c) both electric and magnetic effects

Q.12 An electric dipole of moment 𝑝⃗ is placed in a uniform electric field 𝐸⃗ . Then

(i) the torque on the dipole is 𝑝⃗ ×E→

(ii) the potential energy of the system is 𝑝⃗ .E→

(iii) the resultant force on the dipole is zero. Choose the correct option.

(a) (i), (ii) and (iii) are correct

(b) (i) and (iii) are correct and (ii) is wrong

(d) (i) and (ii) are correct and (iii) is wrong

Answer- (b) (i) and (iii) are correct and (ii) is wrong

Q.13 In a parallel plate capacitor, the capacity increases if

(a) area of the plate is decreased.

(b) distance between the plates increases.

(d) dielectric constantly decreases.

Answer- (c) area of the plate is increased.

Q.14 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

(d) becomes zero

Answer- (a) increases

Q.15 Two spherical conductors each of capacity C are charged to potential V and -V. These are then connected by means of a fine wire. The loss of energy is

(a) zero

(b) ½ CV²

(d) 2 CV²

Answer- (c) CV²

Q.16 Two identical capacitors are joined in parallel, charged to a potential V, separated and then connected in series, the positive plate of one is connected to the negative of the other. Which of the following is true?

(a) The charges on the free plated connected together are destroyed.

(b) The energy stored in this system increases.

(d) The potential difference remains constant.

Answer- (c) The potential difference between the free plates is 2V.

Q.17 In a region, 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 the point (1,1,1) is-

(a) 6√5 N

(b) 30 N

(d) 4√35 N

Answer- (d) 4√35 N

Q.18 An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?

(a) The electron will be accelerated along the axis.
(b) The electron path will be circular about the axis.
(c) The electron will experience a force at 45° to the axis and hence execute a helical path.
(d) The electron will continue to move with uniform velocity along the axis of the solenoid.

Answer: (d) The electron will continue to move with uniform velocity along the axis of the solenoid.

Q.19 Which of the following is not correct about cyclotron?

(a) It is a machine to accelerate charged particles or ions to high energies.
(b) Cyclotron uses both electric and magnetic fields in combination to increase the energy of charged particles.
(c) The operation of the cyclotron is based on the fact that the time for one revolution of an ion is independent of its speed or radius of its orbit.
(d) The charged particles and ions in cyclotron can move on any arbitrary path.

Answer: (d) The charged particles and ions in cyclotron can move on any arbitrary path.

Q.20 Which of the following independent quantities is not used to specify the earth’s magnetic field?

(a) Magnetic declination (θ).

(b) Magnetic dip (δ).

(d) Vertical component of earth’s field (BV).

Answer (d) Vertical component of earth’s field (BV).

Q.21 Which of the following is correct about magnetic monopole?

(a) Magnetic monopole exists.

(b) Magnetic monopole does not exist.

(d) The monopole momentum increase due to an increase in its distance from the field.

Answer (b) Magnetic monopole does not exist.

Q.22 Which of the following is not showing the essential difference between electrostatic shielding by a conducting shell and magnetostatic shielding?

(a) Electrostatic field lines can end on charges and conductors have free charges.

(b) Magnetic field lines can end but conductors cannot end them.

(d) Shells of high permeability materials can be used to divert lines of the magnetic field from the interior region.

Answer- (b) Magnetic field lines can end but conductors cannot end them.

Q.23 The permeability of a paramagnetic substance is:

(a) very large
(b) small but more than unity
(c) less than unity
(d) negative

Answer: (b) small but more than unity

Q.24 The vertical component of earth’s magnetic field . at a place is √3 times the horizontal component
the value of angle of dip at this place is
(a) 30°
(b) 45°
(c) 60°
(d) 90°

Answer: (c) 60°

Q.25 At a given place on earth’s surface the horizontal component of earth’s magnetic field is 2 × 10^3-5 T and resultant magnetic field is 4 × 10^3-5 T. The angle of dip at this place is
(a) 30°
(b) 60°
(c) 90°
(d) 45°

Answer: (b) 60°

Q.26 Which of the following property shows the property of ferromagnetic substances?
(a) The ferromagnetic property depends on temperature
(b) The ferromagnetic property does not depend on temperature.
(c) At high enough temperature ferromagnet becomes a diamagnet.
(d) At low temperature ferromagnet becomes a paramagnet.

Answer: (a) The ferromagnetic property depends on temperature

Q.27 The primary origin of magnetism lies in
(a) atomic current and intrinsic spin of electrons.
(b) polar and non polar nature of molecules.
(c) Pauli exclusion principle.
(d) electronegative nature of materials.

Answer: (a) atomic current and intrinsic spin of electrons.

Q.28 If the coil A is made to rotate about a vertical axis (Figure). No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counter clockwise and the coil A is as shown at this instant, t = 0, is

(a) constant current clockwise.
(b) varying current clockwise.
(c) varying current counterclockwise.
(d) constant current counterclockwise.

Answer: (a) constant current clockwise.

Q.29 A cylindrical bar magnet is rotated about its axis (Figure). A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then

(a) a direct current flows in the ammeter A.
(b) no current flows through the ammeter A.
(c) an alternating sinusoidal current flows through the ammeter A with a time period T = 2πω
(d) a time varying non-sinusoidal current flows through the ammeter.

Answer: (b) no current flows through the ammeter A.

Q.30 Eddy currents do not cause
(a) damping
(b) heating
(c) sparking
(d) loss of energy

Answer: (c) sparking

Q. 31 The electric field intensity due to an infinite cylinder of radius R and having charge q per unit length at a distance rir r(r > R) from its axis is
(a) directly proportional to r².
(b) directly proportional to r³.
(c) inversely proportional to r.
(d) inversely proportional to r².

Answer: (d) inversely proportional to r².

Q.32 In an L.C.R. series a.c. circuit, the current
(a) is always in phase with the voltage
(b) always lags the generator voltage
(c) always leads the generator voltage
(d) None of these

Answer: (d) None of these

Q.33 An LCR series circuit, connected to a source E, is at resonance. Then the voltage across
(a) R is zero
(b) R equals applied voltage
(c) C is zero
(d) L equals applied voltage

Answer: (b) R equals applied voltage

Q.34 The electric field inside a spherical shell of uniform surface charge density is
(a) zero.
(b) constant, less than zero.
(c) directly proportional to the distance from the centre.
(d) none of the these

Answer: (a) zero.

Q.35 Given below are two statements labelled as Assertion (A) and Reason (R)

Assertion: In high latitudes one sees colourful curtains of light hanging down from high altitudes
Reason: The high energy charged particles from the sun are deflected to polar regions by the magnetic field of the earth

Select the most appropriate answer from the options given below:

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A.

(d) A is false and R is also false.

Answer: (a) Both A and R are true and R is the correct explanation of A

Q.36 Given below are two statements labelled as Assertion (A) and Reason (R)

Assertion: A capacitor is connected to a direct current source. Its reactance is infinite.
Reason: Reactance of a capacitor is given by χ_c = 1/ωC.

Select the most appropriate answer from the options given below:

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A.

(d) A is false and R is also false.

Answer: (a) Both A and R are true and R is the correct explanation of A

Q.37 The temperature coefficient of resistance of a wire is 0.00125° C^-1. At 27°C, its resistance is 1Ω. The temperature of the wire at which its resistance becomes 2Ω is:
(a) 1400 K
(b) 854°C
(c) 1127 K
(d) 1154 K.

Answer: (b) 854°C

Q.38 The heating element of an electric heater should be made of a material that should have:
(a) low specific resistance and low melting point.
(b) high specific resistance and high melting point.
(c) high specific resistance and low melting point.
(d) low specific resistance and high melting point.

Answer: (a) low specific resistance and low melting point.

Q. The effective wattage of 60 W and 40 W lamps connected in: series is equal to:
(a) 24 W
(b) 20 W
(c) 100 W
(d) 80 W.

Answer: (a) 24 W

Q.39 The effective wattage of 60 W and 40 W lamps connected in: parallel is equal to:
(a) 24 W
(b) 20 W
(c) 100 W
(d) 80 W

Answer: (a) 24 W

Q.40 At resonance frequency the impedance in series LCR circuit is
(a) maximum
(b) minimum
(c) zero
(d) infinity

Answer: (b) minimum

Q.41 At resonant frequency the current amplitude in series LCR circuit is
(a) maximum
(b) minimum
(c) zero
(d) infinity

Answer: (a) maximum

Q.42 In tuning, we vary the capacitance of a capacitor in the tunning circuit such that the resonant frequency of the circuit becomes nearly equal to the frequency of the radio signal received. When this happens, the …A… with the frequency of the signal of the particular radio station in the circuit is maximum. Here A refers to
(a) resonant frequency
(b) impedance
(c) amplitude of the current
(d) reactance

Answer: (c) amplitude of the current

Q. 43 What is the angle of dip at a place where the horizontal component of earth’s magnetic field is equal to the vertical component?
(a) 0°
(b) 30°
(c) 45°
(d) 90°

Answer: (c) 45°

Q.44 Which of the following has a low value in ferrites?
(a) Conductivity
(b) Permeability
(c) Magnetic susceptibility
(d) All the above

Answer: (a) Conductivity

Q.45 S.I. unit of flux is :
(a) Ohm
(b) Weber
(c) Tesla
(d) None

Answer: (b) Weber

Q.46 The dimensional representation of magnetic flux density is :
(a) [MLT^-2]
(b) [MLT^-2A^-1]
(c) [MLT^-2A^-2]
(d) [MT^-2A^-1]

Answer: (b) [MLT^-2A^-1]

Q.47 A loop, made of straight edges has six comers at A(0, 0, 0), B(L, 0, 0) C(L, L, 0), D(0, L, 0), E(0, L, L) and F(0,0, L). A magnetic field B = B_o (i+k)T is present in the region. The flux passing through the loop ABCDEFA (in that order) is

(a) B_oL² Wb.
(b) 2B_oL² Wb.
(c) √2B_oL² Wb.
(d) 4B_oL² Wb.

Answer: (b) 2B_oL² Wb.

Q.48 An e.m.f is produced in a coil, which is not connected to an external voltage source. This is not due to
(a) the coil being in a time varying magnetic field.
(b) the coil moving in a time varying magnetic field.
(c) the coil moving in a constant magnetic field.
(d) the coil is stationary in external spatially varying magnetic field, which does not change with time.

Answer: (d) the coil is stationary in external spatially varying magnetic field, which does not change with time.

Q.49 Given below are two statements labelled as Assertion (A) and Reason (R)

Assertion(A) The field intensity in between such sheets having equal and opposite uniform surface densities of charge become constant.

Reason(R): The field intensity does not depend upon the distance between the thin sheet.

Select the most appropriate answer from the options given below:

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A.

(d) A is false and R is also false.

Answer: (a) Both A and R are true and R is the correct explanation of A

Q.50 Given below are two statements labelled as Assertion (A) and Reason (R)

Assertion : In series LCR resonance circuit, the impedance is equal to the ohmic resistance.
Reason: At resonance, the inductive reactance exceeds the capacitive reactance.

Select the most appropriate answer from the options given below:

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A.

(d) A is false and R is also false.

Answer: (b) Both A and R are true but R is not the correct explanation of A.

Q. 51 Given below are two statements labelled as Assertion (A) and Reason (R)

Assertion : A capacitor is connected to a direct current source. Its reactance is infinite.
Reason : Reactance of a capacitor is given by χ_c = 1/ωC.

Select the most appropriate answer from the options given below:

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A.

(d) A is false and R is also false.

Answer: (a) Both A and R are true and R is the correct explanation of A

Q.52 The force per unit charge is known as
(a) electric flux
(b) electric field
(c) electric potential
(d) electric current

Answer: (b) electric field

Q.53 Which of the following statements is not true about Gauss’s law?
(a) Gauss’s law is true for any closed surface.
(b) The term q on the right side side of Gauss’s law includes the sum of all charges enclosed by the surface.
(c) Gauss’s law is not much useful in calculating electrostatic field when the system has some symmetry.
(d) Gauss’s law is based on the inverse square dependence on distance contained in the coulomb’s law

Answer: (c) Gauss’s law is not much useful in calculating electrostatic field when the system has some symmetry.

Q. In a region of constant potential
(a) the electric field is uniform.
(b) the electric field is zero.
(c) there can be no charge inside the region.
(d) both (b) and (c) are correct.

Answer: (d) both (b) and (c) are correct.

Q.54 Consider a uniform electric field in the z-direction. The potential is a constant
(a) for any x for a given z
(b) for any y for a given z
(c) on the x-y plane for a given z
(d) all of these

Answer: (d) all of these

Q.55 Which of the following colours of white light deviated most when passes through a prism?
(a) Red light
(b) Violet light
(c) Yellow light
(d) Both (a) and (b)

Answer: (b) Violet light

Q.56 The conduction current is same as displacement current when source is
(a) ac only
(b) dc only
(c) either ac or dc
(d) neither dc nor ac

Answer: (c) either ac or dc

Q.57 If a conductor has a potential V ≠ 0 and there are no charges anywhere else outside, then
(a) there must be charges on the surface or in¬side itself.
(b) there cannot be any charge in the body of the conductor.
(c) there must be charges only on the surface.
(d) both (a) and (b) are correct.

Answer: (c) there must be charges only on the surface.

Q.58 Alternating voltage (V) is represented by the equation
(a) V(t) = Vm eωt
(b) V(t) = Vm sin ωt
(c) V(t) = Vm cot ωt
(d) V(t) = Vm tan ωt

Answer: (b) V(t) = Vm sin ωt

Q.59 The mobility of conduction electrons is greater than that of holes since electrons is greater than that of holes since electrons.
(a) are negatively charged.
(b) are lighter
(c) require smaller energy for moving through the crystal lattice.
(d) Undergo smaller number of collisions.

Answer: (c) require smaller energy for moving through the crystal lattice.

Q.60 Mirage is a phenomenon due to
(a) refraction of light
(b) reflection of light
(c) total internal reflection of light
(d) diffraction of light.

Answer: (c) total internal reflection of light

Q.61 Photoelectrons are being obtained by irradiating zinc by a radiation of 3100 Å. In order to increase the kinetic energy of ejected photoelectrons.
(a) the intensity of radiation should be increased.
(b) the wave length of radiation should be increased.
(c) the wavelength of radiation should be decreased.
(d) both wavelength and intesity of radiation should be increased.

Answer: (c) the wavelength of radiation should be decreased.

Q.62 In a pure capacitive circuit if the frequency of ac source is doubled, then its capacitive reactance will be
(a) remains same
(b) doubled
(c) halved
(d) zero

Answer: (c) halved

Q.63 If the conductivity of a semiconductor is only due to break of the covalent band due to the thermal excitation, then the semiconductor is called:
(a) intrinsic
(b) extrinsic
(c) Acceptor
(d) none of these

Answer: (a) intrinsic

Q.64 If a variable frequency ac source is connected to a capacitor then with decrease in frequency the displacement current will
(a) increase
(b) decrease
(c) remains constant
(d) first decrease then increase

Answer: (b) decrease

Q.65 Direction of current induced in a wire moving in a magnetic field is found using
(a) Fleming’s left hand rule
(b) Fleming’s right hand rule
(c) Ampere’s rule
(d) Right hand clasp rule

Answer: (b) Fleming’s right hand rule

Q.66 A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, the current will
(a) increase
(b) decrease
(c) remain same
(d) first increase then decrease

Answer: (b) decrease