# CBSE Class 11 Physics Quiz | CBSE Class 11 Physics Multiple Choice Questions(MCQs) with Answers

Questions
61 If a charged particle moves through a magnetic field perpendicular to it
A both momentum and energy of particle change.
B momentum as well as energy are constant.
C energy is constant but momentum changes.
D momentum is constant but energy changes.

Answer: energy is constant but momentum changes.
62 Consider a wire carrying a steady current, I placed in a uniform magnetic field B perpendicular to its length. Consider the charges inside the wire. It is known that magnetic forces do not work. This implies that,
A motion of charges inside the conductor is unaffected by B, since they do not absorb energy.
B Some charges inside the wire move to the surface as a result of B.
C if the wire moves under the influence of B, no work is done by the force.
D If the wire moves under the influence of B, no work is done by the electric force on the ions, assumed fixed within the wire.

Answer: Some charges inside the wire move to the surface as a result of B.
63 A cubical region of space is filled with some uniform electric and magnetic fields. An electron enters the cube across one of its faces with velocity v and a positron enters via opposite face with velocity -v. At this instant,
A the electric forces on both the particles cause identical accelerations.
B the magnetic forces on both the particles cause equal accelerations.
C Only electron gains or looses energy.
D the motion of the centre of mass (CM) is determined by E alone.

Answer: the magnetic forces on both the particles cause equal accelerations.
64 A circular coil of radius 4 cm and of 20 turns carries a current of 3 amperes. It is placed in a magnetic field of intensity of 0.5 weber/m². The magnetic dipole moment of the coil is
A 0.15 ampere-m²
B 0.3 ampere-m²
C 0.45 ampere-m²
D 0.6 ampere-m²

65 In a cyclotron, a charged particle [NCERT Exemplar]
A undergoes acceleration all the time.
B speeds up between the dees because of the magnetic field.
C speeds up in a dee.
D slows down within a dee and speeds up between dees.

Answer: undergoes acceleration all the time.
66 An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true? [NCERT Exemplar]
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: The electron will continue to move with uniform velocity along the axis of the solenoid
67 A current carrying circular loop of radius R is placed in the x-y plane with centre at the origin. Half of the loop with x > 0 is now bent so that it now lies in the y – z plane. [NCERT Exemplar]
A The magnitude of magnetic moment now diminishes.
B The magnetic moment does not change.
C The magnitude of B at (0.0.z), z» R increases.
D The magnitude of B at (0, 0, z), z » R is unchanged.

Answer: The magnitude of magnetic moment now diminishes.
68 If the magnetising field on a ferromagnetic material is increased, its permeability.
A is decreased
B is increased
C is unaffected
D may be increased or decreased.

69 Lines of force, due to earth’s horizontal magnetic field, are
A parallel and straight
B concentric circles
C curved lines
D elliptical

70 Angle of dip is 90° at
A poles.
B tropic of cancer.
C equator.
D both at equator and poles.

71 Curie law xT = constant, relating magnetic susceptibility (x) and absolute temperature (T) of magnetic substance is obeyed by
A all magnetic substances.
B paramagnetic substances.
C diamagnetic substances.
D ferromagnetic substances.

72 The material suitable for making electromagnets should have
A high retentivity and high coercivity.
B low retentivity and low coercivity.
C high retentivity and low coercivity.
D low retentivity and high coercivity.

Answer: high retentivity and low coercivity.
73 Curie temperature is the temperature above which
A a ferromagnetic material becomes paramagnetic.
B a ferromagnetic material becomes diamagnetic.
C a paramagnetic material becomes diamagnetic.
D a paramagnetic material becomes ferromagnetic.

Answer: a ferromagnetic material becomes paramagnetic.
74 Three needles N1 N2 and N3 are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet, when brought close to them, will
A attract N1 strongly, but repel N2 and N3 weakly.
B attract all three of them.
C attract N1 and N2 strongly but repel N3.
D attract N1 strongly, N2 weakly and repel N3 weakly.

Answer: attract N1 strongly, N2 weakly and repel N3 weakly.
75 A magnetic needle is kept in a non-uniform magnetic field. It experiences
A a torque but not a force.
B neither a force nor a torque.
C a force and a torque.
D a force but not a torque.

Answer: a force and a torque.
76 Let the magnetic field on earth be modelled by that of a point magnetic dipole at the centre of earth. The angle of dip at a point on the geographical equator
A is always zero.
B can be zero at specific points.
C cannot be positive or negative.
D is not bounded.

Answer: can be zero at specific points.
77 Essential difference between electrostatic shielding by a conducting shell and magne-tostatic shielding is due to
A electrostatic field lines cannot end on ’ charges and conductors do not have free charges.
B lines of B can also end but conductors cannot end them.
C lines of B cannot end. on any material and perfect shielding is not possible.
D shells of high permeability materials cannot be used to divert lines of B from the interior region.

Answer: lines of B cannot end. on any material and perfect shielding is not possible.
78 A long solenoid has 1000 turns per metre and carries a current of 1 A. It has a soft iron core of μr = 1000. The core is heated beyond the Curie temperature, Tc .
A The H field in the solenoid is (nearly) unchanged but the B field decreases drastically.
B The H and B fields in the solenoid are nearly unchanged.
C The magnetisation in the core reverses direction.
D The magnetisation in the core does not diminishes.

Answer: The H field in the solenoid is (nearly) unchanged but the B field decreases drastically.
79 The primary origin(s) of magnetism lies in
A Pauli exclusion principle.
B polar nature of molecules.
C intrinsic spin of electron.
D None of these.