# MCQ Question for Class 12 Physics Chapter 4 Moving Charges and Magnetism

Refer to MCQ Class 12 Moving Charges and Magnetism provided below which is an important chapter in Class 12 Physics. Students should go through the MCQs questions for Class 12 Physics Chapter 4 Moving Charges and Magnetism with answers given below so that they are able to understand the complete topic properly. It’s important to understand the entire chapter by reading Class 12 Physics Notes also. Also, refer to MCQ Questions for Class 12 Physics for all chapters.

## MCQ on Moving Charges and Magnetism Class 12 Physics PDF with Answers

All multiple choice questions with solutions provided below have been developed based on the latest syllabus and examination pattern issued for class 12 by CBSE and NCERT. As Moving Charges and Magnetism is a very important and scoring chapter in Physics Class 12, therefore, the students should carefully learn the questions and answers given below which will help them to get better scores in upcoming examinations for class 12th.

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. A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is
(a) B/2
(b) B
(c) 2 B
(d) 4 B

B

Question. Two long parallel wires are at a distance of 1 metre.
Both of them carry one ampere of current. The force of attraction per unit length between the two wires is
(a) 5 × 10–8 N/m
(b) 2 × 10–8 N/m
(c) 2 × 10–7 N/m
(d) 10–7 N/m

C

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 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. 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. If a long hollow copper pipe carries a current, then produced magnetic field will be
(a) both inside and outside the pipe
(b) outside the pipe only
(c) inside the pipe only
(d) neither inside nor outside the pipe.

B

Question. The magnetic field at a distance r from a long wire carrying current i is 0.4 tesla. The magnetic field at a distance 2r is
(a) 0.2 tesla
(b) 0.8 tesla
(c) 0.1 tesla
(d) 1.6 tesla

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. 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. 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. 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 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. 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 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 galvanometer of resistance, G, is shunted by a resistance S ohm. To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is
(a) G /(S +G)
(b) S2 /(S +G)
(c) SG /(S +G)
(d) G2/ (S +G )

D

Question. Magnetic field intensity at the centre of the coil of 50 turns, radius 0.5 m and carrying a current of 2 A, is
(a) 3 × 10–5 T
(b) 1.25 × 10–4 T
(c) 0.5 × 10–5 T
(d) 4 × 106 T

B

Question. A coil of one turn is made of a wire of certain length and then from the same length a coil of two turns is made. If the same current is passed in both the cases, then the ratio of the magnetic inductions at their centres will be
(a) 4 : 1
(b) 1 : 4
(c) 2 : 1
(d) 1 : 2

B

Question. A galvanometer has a coil of resistance 100 ohm and gives a full scale deflection for 30 mA current. If it is work as a voltmeter of 30 volt range, the resistance required to be added will be
(a) 900 W
(b) 1800 W
(c) 500 W
(d) 1000 W.

A

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 beam of electron passes undeflected through mutually perpendicular electric and magnetic fields.
If the electric field is switched off, and the same magnetic field is maintained, the electrons move
(a) in a circular orbit
(b) along a parabolic path
(c) along a straight line
(d) in an elliptical orbit.

A

Question. A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength 20 V m–1 and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons?
(a) 8 m s–1
(b) 5.5 m s–1
(c) 20 m s–1
(d) 40 m s–1

D

Question. A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the centre of the loop is B. It is then bent into a circular coil of n turns. The magnetic field at the centre of this coil of n turns will be
(a) nB
(b) n2B
(c) 2nB
(d) 2n2B.

B

Question. Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What potential difference in volts should be applied across them so that the magnetic field at their centres is the same?
(a) 2
(b) 3
(c) 4
(d) 6

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. An electron moves in a circular orbit with a uniform speed v. It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to
(a) √B / v
(b) B/v
(c) √v / B
(d) v/B

C

Question. The magnetic field due to a square loop of side a carrying a current I at its centre is
(a) μ0i / 2a
(b) μ0i / √2Πa
(c) μ0i / 2Πa
(d) √2μ0i /Πa

D

Question. Electron of mass m and charge q is travelling with a speed along a circular path of radius r at right angles to a uniform magnetic field of intensity B. If the speed of the electron is doubled and the magnetic field is halved the resulting path would have a radius
(a) 2 r
(b) 4 r
(c) r /4
(d) r/2

B

Question. A long straight wire of radius a carries a steady current I. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields B and B′, at radial distances a/2 and 2a respectively, from the axis of the wire is
(a) 1
(b) 4
(c) 1 /4
(d) 1/2

A

Question. A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by the another wire of 1 mm diameter carrying the same current. The strength of the magnetic field far away is
(a) one-quarter of the earlier value
(b) one-half of the earlier value
(c) twice the earlier value
(d) same as the earlier value.

D

Question. The magnetic induction at a point P which is at the distance of 4 cm from a long current carrying wire is 10–3 T. The field of induction at a distance 12 cm from the current will be
(a) 3.33 × 10–4 T
(b) 1.11 × 10–4 T
(c) 33 × 10–3 T

A

Question. A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is (m0 = 4p × 10–7 T m A–1)
(a) 6.28 × 10–4 T
(b) 3.14 × 10–4 T
(c) 6.28 × 10–5 T
(d) 3.14 × 10–5

A

Question. Two toroids 1 and 2 have total number of turns 200 and 100 respectively with average radii 40 cm and 20 cm respectively. If they carry same current i, the radio of the magnetic fields along the two loops is
(a) 1 : 1
(b) 4 : 1
(c) 2 : 1
(d) 1 : 2

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. An electron having mass m and kinetic energy E enter in uniform magnetic field B perpendicularly, then its frequency will be
(a) eE /qvB
(b) 2πm /eB
(c) eB /2πm
(d) 2m /eBE

C

Question. Two concentric circular coils of ten turns each are situated in the same plane. Their radii are 20 and 40 cm and they carry respectively 0.2 and 0.4 ampere current in opposite direction. The magnetic field in weber/m2 at the centre is
(a) μ0/80
(b) 7μ0/80
(c) (5/4) μ0
(d) zero

D

Question. Energy in a current carrying coil is stored in the form of
(a) electric field
(b) magnetic field
(c) dielectric strength
(d) heat

B

Question. A uniform electric field and a uniform magnetic field exist in a region in the same direction. An electron is projected with velocity pointed in the same direction. The electron will
(a) turn to its right
(b) turn to its left
(c) keep moving in the same direction but its speed will increase
(d) keep moving in the same direction but its speed will decrease

D

Question. Protons and a-particles of equal momenta enter a uniform magnetic field normally. The radii of their orbits will have the ratio.
(a) 1
(b) 2
(c) 0.5
(d) 4

B

Question. A cathode ray beam is bent in a circle of radius 2 cm by a magnetic induction 4.5 × 10–3 weber/m2. The velocity of electron is
(a) 3.43 × 107 m/s
(b) 5.37 × 107 m/s
(c) 1.23 × 107 m/s
(d) 1.58 × 107 m/s

D

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

B

Question. A current of I ampere flows along an infinitely long straight thin walled hollow metallic cylinder of radius r. The magnetic field at any point inside the cylinder at a distance x from the axis of the cylinder is

D

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. A wire of length L metre carrying a current I ampere is bent in the form of a circle. Its magnitude of magnetic moment will be
(a) IL/4π
(b) I2L2/4π
(c) IL2/4π
(d) IL2/8π

C

Question. A current of 3 A is flowing in a linear conductor having a length of 40 cm. The conductor is placed in a magnetic field of strength 500 gauss and makes an angle of 30º with the direction of the field. It experiences a force of magnitude
(a) 3 × 10–4 N
(b) 3 × 10–2 N
(c) 3 × 102 N
(d) 3 × 104 N

B

Question. If a straight current carrying wire is suspended horizontally in mid-air by a uniform magnetic field, then what could be the possible reason for it?
(a) The gravitational force is balanced by electric field produced by wire.
(b) The external magnetic field is balanced by magnetic field due to conductor.
(c) The magnetic field produced by conductor is balanced by magnetic field of Earth.
(d) The gravitational force on the conductor is balanced by external magnetic field.

D

Question. According to Biot Savart’s law, the magnetic field produced by a current carrying conductor is perpendicular to the plane containing:
(a) r
(b) Idl
(c) the conductor
(d) r and Idl

D

Question. A horizontal overhead power line carries a current of 90 A in east to west direction. What are the magnitude and direction of the magnetic field due to this current 1.5 m below the line?
(a) 1.2 x 10-5T perpendicularly outwards to the plane of paper
(b) 1.9 x 10-5T perpendicularly outwards to the plane of paper
(c) 2.6x 10-5T perpendicularly inwards to the plane of paper
(d)2.6 x 10-5T perpendicularly outwards to the plane of paper

A

Question. If the force per unit length between two long straight wires carrying currents 4 A and 6 A is 1.6 X 10-4 N/m, then the distance between the wires is
(a) 5 cm
(b) 3 cm
(c) 3 m
(d) 1 cm

B

Question. Which of the following is an incorrect formula for magnetic force experienced by a conductor in magnetic field? Options are not readable due to notation
(a) I (LXB)
(b) (jAL) X B
(c) nALqvd X B
(d) I (jL X B)

D

Question. As per Ampere’s circuital law, the magnetic field at every point on a circle of radius r, HAVING current carrying wire along the axis, possesses ____________symmetry.
(a) spherical
(b) Linear
(c) cylindrical
(d) none of these

C

Question. A galvanometer cannot be used as such as an ammeter because
(a) it has low resistance
(b) it has low sensitivity
(c) it has high resistance
(d) it is not well calibrated always.

C

Question. The value of gyromagnetic ratio, μ/𝑙 = 𝑒/2𝑚’ for an electron is:
(a) 6.6 X 10-34 C/kg
(b) 8.8 X 1010 C/Kg
(c) 8.85 X 1012 C/kg
(d) 1.6 X 10-19 C/kg

B

Question. In definition of 1 A, the force between two very long, straight, parallel conductors of negligible cross-section, placed 1 m apart in vacuum is
(a) 2 X 10-7 N
(b) 0.2 X 10 N
(c) 20 X 10 N
(d) None of the above

D

Question. ‘Parallel current CARRYING WIRES__________ and antiparallel current CARRYING WIRES ____________.
(a) attract, repel
(b) repel,attract
(c) attract, attract
(d) repel,repel

A

Question. If magnetic field inside a solenoid is 15 T, then what will be the approximate magnetic field near its one end?
(a) 30 T
(b) 7.5 T
(c) 15 T
(d) 0

B

Question. A galvanometer having a resistance of 9Ω is shunted by a wire of resistance 2 Ω. If the total current is 1A, the part of it passing through the shunt will be
(a) 0.2 A
(b) 0.8 A
(c) 0.25 A
(d) 0.5 A

B

Question. The magnetic force acting on a charged particle having charge -3μC in a magnetic field of 2 T acting in y direction, when the particle velocity is (2𝑖̂ + 3𝑗̂) X 106 m/s is
(a) 12 N in -z direction
(b) 12 N in y direction
(c) 12 N in z direction
(d) 18 N in -z direction.

A

Question. Just as static charges produce electric field, moving charges produce:
(a) Electric field only
(b) magnetic field only
(c) Both electric and magnetic fields
(d) drift velocity

C

Question. Calculate the force experienced by the loop in the given figure:

(a) 17.8 X 10-4 N (Attractive)
(b)7.8 X 10-4 N (Attractive)
(c) 17.8 X 10-6 N (Attractive)
(d) 7.8 X 10-4 N (Repulsive)

B

Question. When a rectangular coil carrying current is suspended in magnetic field, then net force experienced by the coil is:
(a) nIBAsinφ
(b) M X B
(c) zero
(d) nIBA

C

Question. The magnetic field in the outside region of the given figure is :

(a) μ0nI
(b) μ0NI
(c) infinite
(d) zero

D

(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false

Question. Assertion: If an electron and proton move in a uniform magnetic field with same speed in perpendicular direction, then they will experience same force (IN MAGNITUDE)
Reason: These particles have same charges.