# MCQs For NCERT Class 12 Physics Chapter 4 Moving Charges and Magnetism

Please refer to the MCQ Questions for Class 12 Physics Chapter 4 Moving Charges and Magnetism with Answers. The following Moving Charges and Magnetism Class 12 Physics MCQ Questions have been designed based on the latest syllabus and examination pattern for Class 12. Our experts have designed MCQ Questions for Class 12 Physics with Answers for all chapters in your NCERT Class 12 Physics book.

## Moving Charges and Magnetism Class 12 MCQ Questions with Answers

See below Moving Charges and Magnetism Class 12 Physics MCQ Questions, solve the questions and compare your answers with the solutions provided below.

Question. An electron moving with kinetic energy 6.6´10-14 J enters in a magnetic field of 4´10-3T at right angles to it. The radius of its circular path will be nearest to :
(a) 100 cm
(b) 75 cm
(c) 25 cm
(d) 50 cm

D

Question. A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in uniform magnetic field. What should be the energy of an a-particle to describe a circle of same radius in the same field?
(a) 2 MeV
(b) 1 MeV
(c) 0.5 MeV
(d) 4 MeV

B

Question. A charged particle enters a magnetic field H with its initial velocity making an angle of 45° with H.
Then the path of the particle will be:
(a) circle
(b) helical
(c) a straight line
(d) a circle

B

Question. What should be amount of current through the ring of radius of 5 cm so that field at the centre equal to the magnetic field of 7 × 10–5 Wb/m2, is
(a) 0.28 amp
(b) 5.57 amp
(c) 2.8 amp
(d) none of these

B

Question. A closely wound flat circular coil of 25 turns of wire has diameter of 10 cm which carries current of 4 amperes, the magnetic field at the centre of a coil will be :
(a) 1.256´10-3 tesla
(b) 1.679´10-5 tesla
(c) 1.512´10-5 tesla
(d) 2.28´10-4 tesla

A

Question. Under the influence of a uniform magnetic field, a charged particle moves with a constant speed v in a circle of radius R. The time period of rotation of the particle
(a) depends on R and not on v
(b) is independent of both v and R
(c) depends on both v and R
(d) depends on v and not on R.

B

Question. Cyclotron is used to accelerate :
(a) positive ion
(b) negative ion
(c) electron
(d) none of these

A

Question. The magnetic field at a given point is 0.5 × 10–5 Wb m–2. This field is to be annulled by magnetic induction at the centre of a circular conducting loop of radius 5.0 cm . The current required to be flown in the loop is nearly
(a) 0.2 A
(b) 0.4 A
(c) 4A
(d) 40 A

B

Question. An electron is travelling along the x-direction. It encounters a magnetic field in the y-direction.
Its subsequent motion will be :
(a) straight line along the x-direction
(b) a circle in the xz-plane
(c) a circle in the yz-plane
(d) a circle in the xy-plane

B

Question. The cyclotron frequency of an electrons gyrating in a magnetic field of 1 T is approximately :
(a) 28 MHz
(b) 280 MHz
(c) 2.8 MHz
(d) 28 GHz

D

Question. The magnetic moment of current (I) carrying circular coil of radius (r) and number of turns (n) varies as :
(a) 1/r2
(b) 1/r
(c) r
(d) r2

D

Question. A circular coil of radius R carries an electric current. The magnetic field due to the coil at a point on the axis of the coil located at a distance r from the centre of the coil, such that r > > R, varies as
(a) 1/r
(b) 1/r3/2
(c) 1/r2
(d) 1/r3

D

Question. A straight wire of length 0.5 metre and carrying a current of 1.2 ampere is placed in uniform magnetic field of induction 2 tesla. The magnetic field is perpendicular to the length of the wire. The force on the wire is
(a) 2.4 N
(b) 1.2 N
(c) 3.0 N
(d) 2.0 N.

B

Question. Two parallel beams of positrons moving in the same direction will :
(a) repel each other
(b) will not interact with each other
(c) attract each other
(d) be deflected normal to the plane containing the two beams

C

Question. A proton and an a-particle, moving with the same velocity, enter a uniform magnetic field, acting normal to the plane of their motion. The ratio of the radii of the circular paths described by the proton and a-particle is :
(a) 1 : 2
(b) 1 : 4
(c) 4 : 1
(d) 1 : 16

A

Question. A long straight wire of radius a carries a steady current i. The current is uniformly distributed across its cross section. The ratio of the magnetic field at a/2 and 2a is
(a) 1/2
(b) 1/4
(c) 4
(d) 1

D

Question. Ionized hydrogen atoms and a-particles with same momenta enters perpendicular to a constant magnetic field, B. The ratio of their radii of their paths rH : ra will be
(a) 1 : 4
(b) 2 : 1
(c) 1 : 2
(d) 4 : 1

B

Question. Electron moves at right angles to a magnetic field of 1.5 × 10–2 tesla with speed of 6 × 107 m/s.
If the specific charge of the electron is 1.7 × 1011 C/kg. The radius of circular path will be
(a) 3.31 cm
(b) 4.31cm
(c) 1.31 cm
(d) 2.35 cm

D

Question. A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron
(a) will turn towards right of direction of motion
(b) speed will decrease
(c) speed will increase
(d) will turn towards left of direction of motion.

B

Question. The magnetic force acting on a charged particle of charge –2 mC in a magnetic field of 2 T acting in y direction, when the particle velocity is (2^i+ 3^j)×106 ms−1 is
(a) 4 N in z direction
(b) 8 N in y direction
(c) 8 N in z direction
(d) 8 N in –z direction.

D

Question. A charge moving with velocity v in X-direction is subjected to a field of magnetic induction in negative X-direction. As a result, the charge will
(a) remain unaffected
(b) start moving in a circular path Y-Z plane
(c) retard along X-axis
(d) moving along a helical path around X-axis.

A

Question. A proton and an alpha particle both enter a region of uniform magnetic field B, moving at right angles to the field B. If the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is 1 MeV, the energy acquired by the alpha particle will be
(a) 1.5 MeV
(b) 1 MeV
(c) 4 MeV
(d) 0.5 MeV

B

Question. An electron beam passes through a magnetic field of 2 × 10–3 Wb/m2 and an electric field of 1.0 × 104 V/m both acting simultaneously. The path of electron remains undeviated. The speed of electron if the electric field is removed, and the radius of electron path will be respectively
(a) 10 × 106 m/s, 2.43 cm
(b) 2.5 × 106 m/s, 0.43 cm
(c) 5 × 106 m/s, 1.43 cm
(d) none of these

C

Question. A charged particle is released from rest in a region of uniform electric and magnetic fields which are parallel to each other. The particle will move on a:
(a) straight line
(b) circle
(c) helix
(d) cycloid

A

Question. Tesla is the unit of
(a) electric field
(b) magnetic field
(c) electric flux
(d) magnetic flux

B

Question. A charged particle moves through a magnetic field in a direction perpendicular to it. Then the
(a) velocity remains unchanged
(b) speed of the particle remains unchanged
(c) direction of the particle remains unchanged
(d) acceleration remains unchanged

B

Question. If we double the radius of a coil keeping the current through it unchanged, then the magnetic field at any point at a large distance from the centre becomes approximately
(a) double
(b) three times
(c) four times
(d) one-fourth

C

Question. A coil of circular cross-section having 1000 turns and 4 cm2 face area is placed with its axis parallel to a magnetic field which decreases by 10–2 Wb m–2 in 0.01 s. The e.m.f. induced in the coil is:
(a) 400 mV
(b) 200 mV
(c) 4 mV
(d) 0.4 mV

A

Question. A metallic rod of mass per unit length 0.5 kg m–1 is lying horizontally on a smooth inclined plane which makes an angle of 30° with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. The current flowing in the rod to keep it stationary is
(a) 7.14 A
(b) 5.98 A
(c) 14.76 A
(d) 11.32 A

D

Question A long straight wire carries a certain current and produces a magnetic field 2 × 10–4 Wb m–2 at a perpendicular distance of 5 cm from the wire.
An electron situated at 5 cm from the wire moves with a velocity 107 m/s towards the wire along perpendicular to it. The force experienced by the electron will be
(charge on electron 1.6 × 10–19 C)
(a) 3.2 N
(b) 3.2 × 10–16 N
(c) 1.6 × 10–16 N
(d) zero

B

Question. When a charged particle moving with velocity v is subjected to a magnetic field of induction  B , the force on it is non-zero. This implies that
(a) angle between is either zero or 180°
(b) angle between is necessarily 90°
(c) angle between can have any value other than 90°
(d) angle between can have any value other than zero and 180°.

D

Question. A particle of mass m, charge Q and kinetic energy T enters in a transverse uniform magnetic field of  induction    B. After 3 seconds the kinetic energy of the particle will be
(a) T
(b) 4T
(c) 3T
(d) 2T

A

Question. A charged particle moves through a magnetic field
in a direction perpendicular to it. Then the
(a) speed of the particle remains unchanged
(b) direction of the particle remains unchanged
(c) acceleration remains unchanged
(d) velocity remains unchanged.

A

Question. A charge having e/m equal to 108 C/kg and with velocity 3 × 105 m/s enters into a uniform magnetic field B = 0.3 tesla at an angle 30° with direction of field. The radius of curvature will be
(a) 0.01 cm
(b) 0.5 cm
(c) 1 cm
(d) 2 cm

D

Question. A positively charged particle moving due East enters a region of uniform magnetic field directed vertically upwards. This particle will
(a) move in a circular path with a decreased speed
(b) move in a circular path with a uniform speed
(c) get deflected in vertically upward direction
(d) move in circular path with an increased speed.

B

Question. A 10 eV electron is circulating in a plane at right angles to a uniform field at magnetic induction 10–4 Wb/m2 (= 1.0 gauss), the orbital radius of electron is
(a) 11 cm
(b) 18 cm
(c) 12 cm
(d) 16 cm

A

Question. A uniform magnetic field acts right angles to the direction of motion of electrons. As a result, the electron moves in a circular path of radius 2 cm. If the speed of electrons is doubled, then the radius of the circular path will be
(a) 2.0 cm
(b) 0.5 cm
(c) 4.0 cm
(d) 1.0 cm

C

Question. A deuteron of kinetic energy 50 keV is describing a circular orbit of radius 0.5 metre in a plane perpendicular to magnetic field B. The kinetic energy of the proton that describes a circular orbit of radius 0.5 metre in the same plane with the same B is
(a) 25 keV
(b) 50 keV
(c) 200 keV
(d) 100 keV

D

Question. A solenoid of length 1.5 m and 4 cm diameter possesses 10 turns per cm. A current of 5A is flowing through it, the magnetic induction at axis inside the solenoid is (μ0 = 4π x 10 – 7 weber – 1 m – 1)
(a) 4p ´10 -5 gauss
(b) 2p´10-5 gauss
(c) 4p´10-5 tesla
(d) 2p´10-5 tesla

D

Question. An electron (mass = 9 × 10–31 kg, charge = 1.6 × 10–19 C) moving with a velocity of 106 m/s enters a magnetic field. If it describes a circle of radius 0.1m, then strength of magnetic field must be
(a) 4.5 × 10–5 T
(b) 1.4 × 10–5 T
(c) 5.5 × 10–5 T
(d) 2.6 × 10–5 T

C

Question.. A square coil of side a carries a current I. The magnetic field at the centre of the coil is

D

Question. In cyclotron the gyro radius is
(a) proportional to momentum
(b) proportional to energy
(c) inversely proportional to momentum
(d) inversely proportional to energy

A

Question. Magnetic effect of current was discovered by
(b) Oersted
(c) Kirchhoff
(d) Joule

B

Question. A proton, deutron and an a-particle enter a magnetic field perpendicular to field with same velocity. What is the ratio of the radii of circular paths?
(a) 1 : 2 : 2
(b) 2 : 1 : 1
(c) 1 : 1 : 2
(d) 1 : 2 : 1

A

Question. A current carrying coil is subjected to a uniform magnetic field. The coil will orient so that its plane becomes
(a) inclined at 45° to the magnetic field
(b) inclined at any arbitrary angle to the magnetic field
(c) parallel to the magnetic field
(d) perpendicular to the magnetic field

D

Question. If an electron and a proton having same momenta enter perpendicular to a magnetic field, then
(a) curved path of electron and proton will be same (ignoring the sense of revolution)
(b) they will move undeflected
(c) curved path of electron is more curved than that of the proton
(d) path of proton is more curved

A

Question. In cyclotron the charged particle may be accelerated upto energies
(a) Several eV
(b) MeV
(c) BeV
(d) Kev

B

Question. The current sensitivity of a moving coil galvanometer depends on
(a) the number of turns in the coil
(b) moment of inertia of the coil
(c) current sent through galvanometer
(d) eddy current in Al frame

A

Question. In cyclotron the resonance condition is
(a) the frequency of revolution of charged particle is equal to the frequency of A.C. voltage sources
(b) the frequency of revolution of charged particle is equal to the frequency of applied magnetic field
(c) the frequency of revolution of charged particle is equal to the frequency of rotation of earth
(d) the frequency of revolution of charged particle, frequency of A.C. source and frequency of magnetic field are equal

A

Question. The total charge induced in a conducting loop when it is moved in a magnetic field depends on
(a) the rate of change of magnetic flux
(b) initial magnetic flux only
(c) the total change in magnetic flux
(d) final magnetic flux only