# MCQs for Physics Class 12 with Answers Chapter 4 Moving Charges and Magnetism

Students of class 12 Physics should refer to MCQ Questions Class 12 Physics Moving Charges and Magnetism 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 4 Moving Charges and Magnetism MCQ with Answers Class 12 Physics

MCQ Questions Class 12 Physics Moving Charges and Magnetism 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. If a conducting wire carries a direct current through it, the magnetic field associated with the current will be __________ .
(a) both inside and outside the conductor
(b) neither inside nor outside the conductor
(c) only outside the conductor
(d) only inside the conductor

C

Question. 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

D

Question. A compass needle is placed above a straight conducting wire. If current passes through the conducting wire from South to North. Then the deflection of the compass __________ .
(a) is towards West
(b) is towards East
(c) keeps oscillating in East-West direction
(d) no deflection

A

Question. Consider the following statements about the representation of the magnetic field
Statement P: The magnetic field emerging out of the plane of the paper is denoted by a dot .
Statement Q: The magnetic field going into the plane of the paper is denoted by a cross .
(a) Both P and Q are true
(b) P is true, but Q is false
(c) P is false, but Q is true
(d) Both P and Q are false

A

Question. 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.
(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.

A

Question. A cyclotron’s oscillator frequency is 20 MHz. If the radius of its ‘dees’ is 40 cm, what is the kinetic energy (in MeV) of the proton beam produced by the accelerator?
(a) 7 MeV
(b) 13.25 MeV
(c) 28 MeV
(d) 3.5 MeV

B

Question. Consider the following two statements about the Oersted’s experiment.
Statement P: The magnetic field due to a straight current carrying conductor is in the form of circular loops around it.
Statement Q: The magnetic field due to a current carrying conductor is weak at near points from the conductor, compared to the far points.
(a) Both P and Q are true
(b) Both P and Q are false
(c) P is true, but Q is false
(d) P is false, but Q is true

C

Question. Biot-Savart law indicates that the moving electrons (velocity v) produce a magnetic field B such that
(a) B is perpendicular to v
(b) B is parallel to v
(c) it obeys inverse cube law
(d) it is along the line joining the electron and point of observation

A

Question. In an ammeter 4% of the mains current is passing through galvanometer. If the galvanometer is shunted with a 5 Ω resistance, then resistance of galvanometer will be
(a) 116 Ω
(b) 117 Ω
(c) 118 Ω
(d) 120 Ω

D

Question. The sensitivity of a moving coil galvanometer increases with the decrease in:
(a) number of turns
(b) area of coil
(c) magnetic field
(d) torsional rigidity

D

Question. A circular coil of 50 turns and radius 7 cm is placed in a uniform magnetic field of 4 T normal to the plane of the coil. If the current in the coil is 6 A then total torque acting on the coil is
(a) 14.78 N
(b) 0 N
(c) 7.39 N
(d) 3.69 N

B

Question. A micro-ammeter has a resistance of 100 W and a full scale range of 50 mA. It can be used as a higher range ammeter or voltmeter provided resistance is added to it. Pick the correct range and resistance combinations.
(a) 50 V range and 10 kW resistance in series
(b) 10 V range and 200 kW resistance in series
(c) 5 mA range with 1 W resistance in parallel
(d) 10 mA range with 1 W resistance in parallel.

B, C

Question. The gyro-magnetic ratio of an electron in an H-atom, according to Bohr model, is
(a) independent of which orbit it is in
(b) negative
(c) positive
(d) increases with the quantum number n

A, B

Question. A current loop in a magnetic field
(a) can be in equilibrium in one orientation
(b) can be in equilibrium in two orientations, both the equilibrium states are unstable
(c) can be in equilibrium in two orientations, one stable while the other is unstable
(d) experiences a torque whether the field is uniform or non-uniform in all orientations

C

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 voltmeter of range 2V and resistance 300 Ω cannot be converted to an ammeter of range:
(a) 5 mA
(b) 8 mA
(c) 1 A
(d) 10 A

A

Question. A current carrying loop is placed in a uniform magnetic field. The torque acting on it does not depend upon the
(a) shape of the loop
(b) area of the loop
(c) value of current
(d) magnetic field

A

Question. A rectangular coil of length 0.12 m and width 0.1 m having 50 turns of wire is suspended vertically in a uniform magnetic field of strength 0.2 Weber/m2. The coil carries a current of 2 A. If the plane of the coil is inclined at an angle of 30° with the direction of the field, the torque required to keep the coil in stable equilibrium will be
(a) 0.24 Nm
(b) 0.12 Nm
(c) 0.15 Nm
(d) 0.20 Nm

D

Question. Two charged particles traverse identical helical paths in a completely opposite sense in a uniform magnetic field B = B0 k.
(a) They have equal z-components of momenta
(b) They must have equal charges
(c) They necessarily represent a particle, anti-particle pair
(d) The charge to mass ratio satisfy: (e / m)1 + (e / m)2 = 0

D

Question. Two straight long conductors AOB and COD are perpendicular to each other and carry currents I1 and I2. The magnitude of the magnetic induction at a point P at a distance a from the point O in a direction perpendicular to the plane ABCD is

C

Question. The radius of motion of a charged particle oscillating in a magnetic field is
(a) mB / qv
(a) mv / q
(a) mq / vB
(a) qv / mB

B

Question. A coil carrying electric current is placed in uniform magnetic field, then
(a) torque is formed
(b) e.m.f is induced
(c) both (a) and (b) are correct
(d) none of the above

A

Question. When a charged particle moving with velocity v is subjected to a magnetic field of induction B̅, 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. 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 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. A long solenoid carrying a current produces a magnetic field B along its axis. If the current is double and the number of turns per cm is halved, the new value of the magnetic field is
(a) 4 B
(b) B/2
(c) B
(d) 2 B

C

Question. Current i is flowing in a coil of area A & number of turns N, then magnetic moment of the coil is M is equal to
(a) NiA
(b) Ni/A
(c) Ni/√A
(d) N2Ai

A

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. Tesla is the unit of
(a) magnetic flux
(b) magnetic field
(c) magnetic induction
(d)magnetic moment

B

Question. To convert a galvanometer into an ammeter, one needs to connect a
(a) low resistance in parallel
(b) high resistance in parallel
(c) low resistance in series
(d) high resistance in series.

A

Question. 1 Wbm–2 is equal to
(a) 104 G
(b) 102 G
(c) 10–2 G
(d) 10–4 G

A

Question. If a current is passed through a spring then the spring will
(a) expand
(b) compress
(c) remains same
(d) None of these.

B

Question. A helium nucleus makes a full rotation in a circle of radius 0.8 meter in 2 sec. The value of the magnetic field induction B in tesla at the centre of circle will be
(a) 2 x 10 – 19 μ0
(a) 10 – 19 / μ0
(a) 10 – 19 μ0
(a) 2 x 10 – 20 / μ0

C

Question. A circular loop of area 0.02 m2 carrying a current of 10A, is held with its plane perpendicular to a magnetic field induction 0.2 T. The torque acting on the loop is
(a) 0.01 Nm
(b) 0.001 Nm
(c) zero
(d) 0.8 Nm

C

Question. Through two parallel wires A and B, 10A and 2A of currents are passed respectively in opposite directions. If the wire A is infinitely long and the length of the wire B is 2m, then force on the conductor B, which is situated at 10 cm distance from A, will be
(a) 8 × 10–7 N
(b) 8 × 10–5 N
(c) 4 × 10–7 N
(d) 4 × 10–5 N

B

Question. Two particles X and Y having equal charge, after being accelerated through the same potential difference enter a region of uniform magnetic field and describe circular paths of radii R1 and R2 respectively. The ratio of the mass of X to that of Y is

C

Question. What is cyclotron frequency of an electron with an energy of 100 e V in the earth’s magnetic field of 1 × 10–4 weber / m2 if its velocity is perpendicular to magnetic field?
(a) 0.7 MHz
(b) 2.8 MHz
(c) 1.4 MHz
(d) 2.1 MHz

B

Question. A conducting circular loop of radius r carries a constant current i. It is placed in a uniform magnetic field B such that B is perpendicular to the plane of the loop. The magnetic force acting on the loop is :
(a) ir B
(b) 2priB
(c) zero
(d) priB

C

Question. In a cyclotron, a charged particle
(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

A

Question. A circular loop of area 0.02 m2 carrying a current of 10A, is held with its plane perpendicular to a magnetic field induction 0.2 T. The torque acting on the loop is
(a) 0.01 Nm
(b) 0.001 Nm
(c) zero
(d) 0.8 Nm

C

Question. A current carrying loop in the form of a right angle isosceles triangle ABC is placed in a uniform magnetic field acting along AB. If the magnetic force on the arm BC is F, what is the force on the arm AC?

Question. A uniform electric field and 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 direction of motion

B

Question. A square loop, carrying a steady current I, is placed in a horizontal plane near a long straight conductor carrying a steady current I1 at a distance d from the conductor as shown in figure. The loop will experience

(a) a net repulsive force away from the conductor
(b) a net torque acting upward perpendicular to the horizontal plane
(c) a net torque acting downward normal to the horizontal plane
(d) a net attractive force towards the conductor

D

Question. Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency f Hz. The magnitude of magnetic induction at the centre of the ring is

A

Question. Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2 I, respectively. The resultant magnetic field induction at the centre will be

A

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 magnetic needle suspended parallel to a magnetic field requires √3 J of work to turn it through 60°. The torque needed to maintain the needle in this position will be

B

Question. Electron move at right angle 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 circular current loop of magnetic moment M is in an arbitrary orientation in an external magnetic field B. The work done to rotate the loop by 30° about an axis perpendicular to its plane is
(a) MB
(b) √3 (MB/2)
(c) MB/2
(d) zero

D

Question. An infinitely long straight wire contains a uniformly continuous current of 10A. The radius of the wire is 4× 10 –2 m. The magnetic field at 2 × 10 –2 m from the centre of the wire will be:
(a) 0
(b) 2.5 × 10 – 5 T
(c) 5.0 × 10 – 5 T
(d) none of these.

B

Question. A proton moving vertically downward enters a magnetic field pointing towards north. In which direction proton will deflect?
(a) East
(b) West
(c) North
(d) South

A

Question. An electron enters a region where magnetic field (B) and electric field (E) are mutually perpendicular, then
(a) it will always move in the direction of B
(b) it will always move in the direction of E
(c) it always possesses circular motion
(d) it can go undeflected also

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) move along a helical path around X-axis