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CLASS 12 PHYSICS CHAPTER 4: MOVING CHARGES AND MAGNETISM — 119 MCQs

CHAPTER INTRODUCTION Plain-text MCQ question bank based on the attached

NCERT chapter. It covers magnetic force, charged-particle motion,

Biot–Savart law, current loops, Ampere’s law, solenoids, parallel

currents, magnetic dipoles and the moving-coil galvanometer.

Q1. Which statement correctly describes Oersted’s observation? (A) a

current-carrying wire deflects a nearby compass needle (B) It is always

zero (C) It is a scalar with no direction (D) It depends only on gravity

Correct Answer: (A) Explanation: current and magnetism are connected.

Q2. Choose the correct expression or result associated with Oersted’s

observation. (A) a current-carrying wire deflects a nearby compass

needle (B) The reciprocal of the stated quantity (C) The square of the

stated quantity (D) No relation can be stated Correct Answer: (A)

Explanation: current and magnetism are connected.

Q3. Which option should a student remember about Oersted’s observation?

(A) a current-carrying wire deflects a nearby compass needle (B) It

contradicts the chapter’s stated rule (C) It is independent of all

physical quantities (D) It applies only when current is zero Correct

Answer: (A) Explanation: current and magnetism are connected.

Q4. Which choice is consistent with the NCERT chapter’s treatment of

Oersted’s observation? (A) a current-carrying wire deflects a nearby

compass needle (B) It has the opposite direction or dependence (C) It is

unrelated to magnetic phenomena (D) It is never used in calculations

Correct Answer: (A) Explanation: current and magnetism are connected.

Q5. Which statement correctly describes magnetic field around a long

straight wire? (A) concentric circles centred on the wire (B) It is

always zero (C) It is a scalar with no direction (D) It depends only on

gravity Correct Answer: (A) Explanation: the field is tangential to

circles around the wire.

Q6. Choose the correct expression or result associated with magnetic

field around a long straight wire. (A) concentric circles centred on the

wire (B) The reciprocal of the stated quantity (C) The square of the

stated quantity (D) No relation can be stated Correct Answer: (A)

Explanation: the field is tangential to circles around the wire.

Q7. Which option should a student remember about magnetic field around a

long straight wire? (A) concentric circles centred on the wire (B) It

contradicts the chapter’s stated rule (C) It is independent of all

physical quantities (D) It applies only when current is zero Correct

Answer: (A) Explanation: the field is tangential to circles around the

wire.

Q8. Which choice is consistent with the NCERT chapter’s treatment of

magnetic field around a long straight wire? (A) concentric circles

centred on the wire (B) It has the opposite direction or dependence (C)

It is unrelated to magnetic phenomena (D) It is never used in

calculations Correct Answer: (A) Explanation: the field is tangential to

circles around the wire.

Q9. Which statement correctly describes dot convention? (A) field

emerging out of the page (B) It is always zero (C) It is a scalar with

no direction (D) It depends only on gravity Correct Answer: (A)

Explanation: a dot represents the tip of an arrow pointing towards the

observer.

Q10. Choose the correct expression or result associated with dot

convention. (A) field emerging out of the page (B) The reciprocal of the

stated quantity (C) The square of the stated quantity (D) No relation

can be stated Correct Answer: (A) Explanation: a dot represents the tip

of an arrow pointing towards the observer.

Q11. Which option should a student remember about dot convention? (A)

field emerging out of the page (B) It contradicts the chapter’s stated

rule (C) It is independent of all physical quantities (D) It applies

only when current is zero Correct Answer: (A) Explanation: a dot

represents the tip of an arrow pointing towards the observer.

Q12. Which choice is consistent with the NCERT chapter’s treatment of

dot convention? (A) field emerging out of the page (B) It has the

opposite direction or dependence (C) It is unrelated to magnetic

phenomena (D) It is never used in calculations Correct Answer: (A)

Explanation: a dot represents the tip of an arrow pointing towards the

observer.

Q13. Which statement correctly describes magnetic field? (A) vector

quantity (B) It is always zero (C) It is a scalar with no direction (D)

It depends only on gravity Correct Answer: (A) Explanation: magnetic

field has magnitude and direction.

Q14. Choose the correct expression or result associated with magnetic

field. (A) vector quantity (B) The reciprocal of the stated quantity (C)

The square of the stated quantity (D) No relation can be stated Correct

Answer: (A) Explanation: magnetic field has magnitude and direction.

Q15. Which option should a student remember about magnetic field? (A)

vector quantity (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: magnetic field has magnitude

and direction.

Q16. Which choice is consistent with the NCERT chapter’s treatment of

magnetic field? (A) vector quantity (B) It has the opposite direction or

dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: magnetic field has

magnitude and direction.

Q17. Which statement correctly describes superposition? (A) vector

addition of individual fields (B) It is always zero (C) It is a scalar

with no direction (D) It depends only on gravity Correct Answer: (A)

Explanation: magnetic fields from multiple sources add vectorially.

Q18. Choose the correct expression or result associated with

superposition. (A) vector addition of individual fields (B) The

reciprocal of the stated quantity (C) The square of the stated quantity

(D) No relation can be stated Correct Answer: (A) Explanation: magnetic

fields from multiple sources add vectorially.

Q19. Which option should a student remember about superposition? (A)

vector addition of individual fields (B) It contradicts the chapter’s

stated rule (C) It is independent of all physical quantities (D) It

applies only when current is zero Correct Answer: (A) Explanation:

magnetic fields from multiple sources add vectorially.

Q20. Which choice is consistent with the NCERT chapter’s treatment of

superposition? (A) vector addition of individual fields (B) It has the

opposite direction or dependence (C) It is unrelated to magnetic

phenomena (D) It is never used in calculations Correct Answer: (A)

Explanation: magnetic fields from multiple sources add vectorially.

Q21. Which statement correctly describes Lorentz force? (A) F = q(E + v

× B) (B) It is always zero (C) It is a scalar with no direction (D) It

depends only on gravity Correct Answer: (A) Explanation: the expression

combines electric and magnetic force.

Q22. Choose the correct expression or result associated with Lorentz

force. (A) F = q(E + v × B) (B) The reciprocal of the stated quantity

(C) The square of the stated quantity (D) No relation can be stated

Correct Answer: (A) Explanation: the expression combines electric and

magnetic force.

Q23. Which option should a student remember about Lorentz force? (A) F =

q(E + v × B) (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: the expression combines

electric and magnetic force.

Q24. Which choice is consistent with the NCERT chapter’s treatment of

Lorentz force? (A) F = q(E + v × B) (B) It has the opposite direction or

dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: the expression

combines electric and magnetic force.

Q25. Which statement correctly describes magnetic force magnitude? (A)

|q|vB sin θ (B) It is always zero (C) It is a scalar with no direction

(D) It depends only on gravity Correct Answer: (A) Explanation: the

cross product introduces the sine of the angle.

Q26. Choose the correct expression or result associated with magnetic

force magnitude. (A) |q|vB sin θ (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: the cross product introduces the

sine of the angle.

Q27. Which option should a student remember about magnetic force

magnitude? (A) |q|vB sin θ (B) It contradicts the chapter’s stated rule

(C) It is independent of all physical quantities (D) It applies only

when current is zero Correct Answer: (A) Explanation: the cross product

introduces the sine of the angle.

Q28. Which choice is consistent with the NCERT chapter’s treatment of

magnetic force magnitude? (A) |q|vB sin θ (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: the cross

product introduces the sine of the angle.

Q29. Which statement correctly describes parallel v and B? (A) zero

magnetic force (B) It is always zero (C) It is a scalar with no

direction (D) It depends only on gravity Correct Answer: (A)

Explanation: the cross product vanishes for parallel vectors.

Q30. Choose the correct expression or result associated with parallel v

and B. (A) zero magnetic force (B) The reciprocal of the stated quantity

(C) The square of the stated quantity (D) No relation can be stated

Correct Answer: (A) Explanation: the cross product vanishes for parallel

vectors.

Q31. Which option should a student remember about parallel v and B? (A)

zero magnetic force (B) It contradicts the chapter’s stated rule (C) It

is independent of all physical quantities (D) It applies only when

current is zero Correct Answer: (A) Explanation: the cross product

vanishes for parallel vectors.

Q32. Which choice is consistent with the NCERT chapter’s treatment of

parallel v and B? (A) zero magnetic force (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: the cross

product vanishes for parallel vectors.

Q33. Which statement correctly describes stationary charge in B? (A)

zero magnetic force (B) It is always zero (C) It is a scalar with no

direction (D) It depends only on gravity Correct Answer: (A)

Explanation: magnetic force depends on velocity.

Q34. Choose the correct expression or result associated with stationary

charge in B. (A) zero magnetic force (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: magnetic force depends on

velocity.

Q35. Which option should a student remember about stationary charge in

B? (A) zero magnetic force (B) It contradicts the chapter’s stated rule

(C) It is independent of all physical quantities (D) It applies only

when current is zero Correct Answer: (A) Explanation: magnetic force

depends on velocity.

Q36. Which choice is consistent with the NCERT chapter’s treatment of

stationary charge in B? (A) zero magnetic force (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: magnetic

force depends on velocity.

Q37. Which statement correctly describes magnetic-force direction? (A)

perpendicular to both v and B (B) It is always zero (C) It is a scalar

with no direction (D) It depends only on gravity Correct Answer: (A)

Explanation: the force direction follows the vector product.

Q38. Choose the correct expression or result associated with

magnetic-force direction. (A) perpendicular to both v and B (B) The

reciprocal of the stated quantity (C) The square of the stated quantity

(D) No relation can be stated Correct Answer: (A) Explanation: the force

direction follows the vector product.

Q39. Which option should a student remember about magnetic-force

direction? (A) perpendicular to both v and B (B) It contradicts the

chapter’s stated rule (C) It is independent of all physical quantities

(D) It applies only when current is zero Correct Answer: (A)

Explanation: the force direction follows the vector product.

Q40. Which choice is consistent with the NCERT chapter’s treatment of

magnetic-force direction? (A) perpendicular to both v and B (B) It has

the opposite direction or dependence (C) It is unrelated to magnetic

phenomena (D) It is never used in calculations Correct Answer: (A)

Explanation: the force direction follows the vector product.

Q41. Which statement correctly describes magnetic field unit? (A) tesla

(B) It is always zero (C) It is a scalar with no direction (D) It

depends only on gravity Correct Answer: (A) Explanation: the SI unit of

magnetic field is tesla.

Q42. Choose the correct expression or result associated with magnetic

field unit. (A) tesla (B) The reciprocal of the stated quantity (C) The

square of the stated quantity (D) No relation can be stated Correct

Answer: (A) Explanation: the SI unit of magnetic field is tesla.

Q43. Which option should a student remember about magnetic field unit?

(A) tesla (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: the SI unit of magnetic field

is tesla.

Q44. Which choice is consistent with the NCERT chapter’s treatment of

magnetic field unit? (A) tesla (B) It has the opposite direction or

dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: the SI unit of

magnetic field is tesla.

Q45. Which statement correctly describes gauss conversion? (A) 1 gauss =

10⁻⁴ T (B) It is always zero (C) It is a scalar with no direction (D) It

depends only on gravity Correct Answer: (A) Explanation: the chapter

states that one gauss is 10⁻⁴ tesla.

Q46. Choose the correct expression or result associated with gauss

conversion. (A) 1 gauss = 10⁻⁴ T (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: the chapter states that one

gauss is 10⁻⁴ tesla.

Q47. Which option should a student remember about gauss conversion? (A)

1 gauss = 10⁻⁴ T (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: the chapter states that one

gauss is 10⁻⁴ tesla.

Q48. Which choice is consistent with the NCERT chapter’s treatment of

gauss conversion? (A) 1 gauss = 10⁻⁴ T (B) It has the opposite direction

or dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: the chapter states

that one gauss is 10⁻⁴ tesla.

Q49. Which statement correctly describes force on a straight conductor?

(A) F = Iℓ × B (B) It is always zero (C) It is a scalar with no

direction (D) It depends only on gravity Correct Answer: (A)

Explanation: the conductor’s length vector points along conventional

current.

Q50. Choose the correct expression or result associated with force on a

straight conductor. (A) F = Iℓ × B (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: the conductor’s length vector

points along conventional current.

Q51. Which option should a student remember about force on a straight

conductor? (A) F = Iℓ × B (B) It contradicts the chapter’s stated rule

(C) It is independent of all physical quantities (D) It applies only

when current is zero Correct Answer: (A) Explanation: the conductor’s

length vector points along conventional current.

Q52. Which choice is consistent with the NCERT chapter’s treatment of

force on a straight conductor? (A) F = Iℓ × B (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: the

conductor’s length vector points along conventional current.

Q53. Which statement correctly describes magnetic work? (A) zero work

(B) It is always zero (C) It is a scalar with no direction (D) It

depends only on gravity Correct Answer: (A) Explanation: magnetic force

is perpendicular to instantaneous velocity.

Q54. Choose the correct expression or result associated with magnetic

work. (A) zero work (B) The reciprocal of the stated quantity (C) The

square of the stated quantity (D) No relation can be stated Correct

Answer: (A) Explanation: magnetic force is perpendicular to

instantaneous velocity.

Q55. Which option should a student remember about magnetic work? (A)

zero work (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: magnetic force is perpendicular

to instantaneous velocity.

Q56. Which choice is consistent with the NCERT chapter’s treatment of

magnetic work? (A) zero work (B) It has the opposite direction or

dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: magnetic force is

perpendicular to instantaneous velocity.

Q57. Which statement correctly describes circular orbit radius? (A) r =

mv/(|q|B) (B) It is always zero (C) It is a scalar with no direction (D)

It depends only on gravity Correct Answer: (A) Explanation: equating

centripetal force and magnetic force gives the radius.

Q58. Choose the correct expression or result associated with circular

orbit radius. (A) r = mv/(|q|B) (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: equating centripetal force and

magnetic force gives the radius.

Q59. Which option should a student remember about circular orbit radius?

(A) r = mv/(|q|B) (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: equating centripetal force and

magnetic force gives the radius.

Q60. Which choice is consistent with the NCERT chapter’s treatment of

circular orbit radius? (A) r = mv/(|q|B) (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: equating

centripetal force and magnetic force gives the radius.

Q61. Which statement correctly describes cyclotron angular frequency?

(A) ω = |q|B/m (B) It is always zero (C) It is a scalar with no

direction (D) It depends only on gravity Correct Answer: (A)

Explanation: the non-relativistic angular frequency does not depend on

speed.

Q62. Choose the correct expression or result associated with cyclotron

angular frequency. (A) ω = |q|B/m (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: the non-relativistic angular

frequency does not depend on speed.

Q63. Which option should a student remember about cyclotron angular

frequency? (A) ω = |q|B/m (B) It contradicts the chapter’s stated rule

(C) It is independent of all physical quantities (D) It applies only

when current is zero Correct Answer: (A) Explanation: the

non-relativistic angular frequency does not depend on speed.

Q64. Which choice is consistent with the NCERT chapter’s treatment of

cyclotron angular frequency? (A) ω = |q|B/m (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: the

non-relativistic angular frequency does not depend on speed.

Q65. Which statement correctly describes helical pitch? (A) p = v∥T (B)

It is always zero (C) It is a scalar with no direction (D) It depends

only on gravity Correct Answer: (A) Explanation: pitch is distance

advanced along the field in one revolution.

Q66. Choose the correct expression or result associated with helical

pitch. (A) p = v∥T (B) The reciprocal of the stated quantity (C) The

square of the stated quantity (D) No relation can be stated Correct

Answer: (A) Explanation: pitch is distance advanced along the field in

one revolution.

Q67. Which option should a student remember about helical pitch? (A) p =

v∥T (B) It contradicts the chapter’s stated rule (C) It is independent

of all physical quantities (D) It applies only when current is zero

Correct Answer: (A) Explanation: pitch is distance advanced along the

field in one revolution.

Q68. Which choice is consistent with the NCERT chapter’s treatment of

helical pitch? (A) p = v∥T (B) It has the opposite direction or

dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: pitch is distance

advanced along the field in one revolution.

Q69. Which statement correctly describes Biot–Savart law? (A) dB =

(μ₀/4π) I(dℓ × r)/r³ (B) It is always zero (C) It is a scalar with no

direction (D) It depends only on gravity Correct Answer: (A)

Explanation: the law gives the field due to a current element.

Q70. Choose the correct expression or result associated with Biot–Savart

law. (A) dB = (μ₀/4π) I(dℓ × r)/r³ (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: the law gives the field due to a

current element.

Q71. Which option should a student remember about Biot–Savart law? (A)

dB = (μ₀/4π) I(dℓ × r)/r³ (B) It contradicts the chapter’s stated rule

(C) It is independent of all physical quantities (D) It applies only

when current is zero Correct Answer: (A) Explanation: the law gives the

field due to a current element.

Q72. Which choice is consistent with the NCERT chapter’s treatment of

Biot–Savart law? (A) dB = (μ₀/4π) I(dℓ × r)/r³ (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: the law

gives the field due to a current element.

Q73. Which statement correctly describes Biot–Savart angular factor? (A)

sin θ (B) It is always zero (C) It is a scalar with no direction (D) It

depends only on gravity Correct Answer: (A) Explanation: the field

contribution vanishes when dℓ is parallel to r.

Q74. Choose the correct expression or result associated with Biot–Savart

angular factor. (A) sin θ (B) The reciprocal of the stated quantity (C)

The square of the stated quantity (D) No relation can be stated Correct

Answer: (A) Explanation: the field contribution vanishes when dℓ is

parallel to r.

Q75. Which option should a student remember about Biot–Savart angular

factor? (A) sin θ (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: the field contribution vanishes

when dℓ is parallel to r.

Q76. Which choice is consistent with the NCERT chapter’s treatment of

Biot–Savart angular factor? (A) sin θ (B) It has the opposite direction

or dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: the field

contribution vanishes when dℓ is parallel to r.

Q77. Which statement correctly describes field at centre of circular

loop? (A) B = μ₀I/(2R) (B) It is always zero (C) It is a scalar with no

direction (D) It depends only on gravity Correct Answer: (A)

Explanation: the centre-field formula follows from the axial formula at

x = 0.

Q78. Choose the correct expression or result associated with field at

centre of circular loop. (A) B = μ₀I/(2R) (B) The reciprocal of the

stated quantity (C) The square of the stated quantity (D) No relation

can be stated Correct Answer: (A) Explanation: the centre-field formula

follows from the axial formula at x = 0.

Q79. Which option should a student remember about field at centre of

circular loop? (A) B = μ₀I/(2R) (B) It contradicts the chapter’s stated

rule (C) It is independent of all physical quantities (D) It applies

only when current is zero Correct Answer: (A) Explanation: the

centre-field formula follows from the axial formula at x = 0.

Q80. Which choice is consistent with the NCERT chapter’s treatment of

field at centre of circular loop? (A) B = μ₀I/(2R) (B) It has the

opposite direction or dependence (C) It is unrelated to magnetic

phenomena (D) It is never used in calculations Correct Answer: (A)

Explanation: the centre-field formula follows from the axial formula at

x = 0.

Q81. Which statement correctly describes Ampere’s circuital law? (A)

∮B·dℓ = μ₀I enclosed (B) It is always zero (C) It is a scalar with no

direction (D) It depends only on gravity Correct Answer: (A)

Explanation: the closed-loop integral is related to the enclosed

current.

Q82. Choose the correct expression or result associated with Ampere’s

circuital law. (A) ∮B·dℓ = μ₀I enclosed (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: the closed-loop integral is

related to the enclosed current.

Q83. Which option should a student remember about Ampere’s circuital

law? (A) ∮B·dℓ = μ₀I enclosed (B) It contradicts the chapter’s stated

rule (C) It is independent of all physical quantities (D) It applies

only when current is zero Correct Answer: (A) Explanation: the

closed-loop integral is related to the enclosed current.

Q84. Which choice is consistent with the NCERT chapter’s treatment of

Ampere’s circuital law? (A) ∮B·dℓ = μ₀I enclosed (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: the

closed-loop integral is related to the enclosed current.

Q85. Which statement correctly describes long straight wire field? (A) B

= μ₀I/(2πr) (B) It is always zero (C) It is a scalar with no direction

(D) It depends only on gravity Correct Answer: (A) Explanation: the

field varies directly with current and inversely with distance.

Q86. Choose the correct expression or result associated with long

straight wire field. (A) B = μ₀I/(2πr) (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: the field varies directly with

current and inversely with distance.

Q87. Which option should a student remember about long straight wire

field? (A) B = μ₀I/(2πr) (B) It contradicts the chapter’s stated rule

(C) It is independent of all physical quantities (D) It applies only

when current is zero Correct Answer: (A) Explanation: the field varies

directly with current and inversely with distance.

Q88. Which choice is consistent with the NCERT chapter’s treatment of

long straight wire field? (A) B = μ₀I/(2πr) (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: the field

varies directly with current and inversely with distance.

Q89. Which statement correctly describes field inside uniform wire? (A)

B ∝ r (B) It is always zero (C) It is a scalar with no direction (D) It

depends only on gravity Correct Answer: (A) Explanation: the enclosed

current is proportional to r².

Q90. Choose the correct expression or result associated with field

inside uniform wire. (A) B ∝ r (B) The reciprocal of the stated quantity

(C) The square of the stated quantity (D) No relation can be stated

Correct Answer: (A) Explanation: the enclosed current is proportional to

r².

Q91. Which option should a student remember about field inside uniform

wire? (A) B ∝ r (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: the enclosed current is

proportional to r².

Q92. Which choice is consistent with the NCERT chapter’s treatment of

field inside uniform wire? (A) B ∝ r (B) It has the opposite direction

or dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: the enclosed

current is proportional to r².

Q93. Which statement correctly describes long solenoid field? (A) B =

μ₀nI (B) It is always zero (C) It is a scalar with no direction (D) It

depends only on gravity Correct Answer: (A) Explanation: n is the number

of turns per unit length.

Q94. Choose the correct expression or result associated with long

solenoid field. (A) B = μ₀nI (B) The reciprocal of the stated quantity

(C) The square of the stated quantity (D) No relation can be stated

Correct Answer: (A) Explanation: n is the number of turns per unit

length.

Q95. Which option should a student remember about long solenoid field?

(A) B = μ₀nI (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: n is the number of turns per

unit length.

Q96. Which choice is consistent with the NCERT chapter’s treatment of

long solenoid field? (A) B = μ₀nI (B) It has the opposite direction or

dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: n is the number of

turns per unit length.

Q97. Which statement correctly describes parallel current interaction?

(A) same-direction currents attract (B) It is always zero (C) It is a

scalar with no direction (D) It depends only on gravity Correct Answer:

(A) Explanation: parallel currents attract and antiparallel currents

repel.

Q98. Choose the correct expression or result associated with parallel

current interaction. (A) same-direction currents attract (B) The

reciprocal of the stated quantity (C) The square of the stated quantity

(D) No relation can be stated Correct Answer: (A) Explanation: parallel

currents attract and antiparallel currents repel.

Q99. Which option should a student remember about parallel current

interaction? (A) same-direction currents attract (B) It contradicts the

chapter’s stated rule (C) It is independent of all physical quantities

(D) It applies only when current is zero Correct Answer: (A)

Explanation: parallel currents attract and antiparallel currents repel.

Q100. Which choice is consistent with the NCERT chapter’s treatment of

parallel current interaction? (A) same-direction currents attract (B) It

has the opposite direction or dependence (C) It is unrelated to magnetic

phenomena (D) It is never used in calculations Correct Answer: (A)

Explanation: parallel currents attract and antiparallel currents repel.

Q101. Which statement correctly describes magnetic moment of loop? (A) m

= NIA (B) It is always zero (C) It is a scalar with no direction (D) It

depends only on gravity Correct Answer: (A) Explanation: the magnetic

moment equals turns times current times area.

Q102. Choose the correct expression or result associated with magnetic

moment of loop. (A) m = NIA (B) The reciprocal of the stated quantity

(C) The square of the stated quantity (D) No relation can be stated

Correct Answer: (A) Explanation: the magnetic moment equals turns times

current times area.

Q103. Which option should a student remember about magnetic moment of

loop? (A) m = NIA (B) It contradicts the chapter’s stated rule (C) It is

independent of all physical quantities (D) It applies only when current

is zero Correct Answer: (A) Explanation: the magnetic moment equals

turns times current times area.

Q104. Which choice is consistent with the NCERT chapter’s treatment of

magnetic moment of loop? (A) m = NIA (B) It has the opposite direction

or dependence (C) It is unrelated to magnetic phenomena (D) It is never

used in calculations Correct Answer: (A) Explanation: the magnetic

moment equals turns times current times area.

Q105. Which statement correctly describes torque on magnetic dipole? (A)

τ = mB sin θ (B) It is always zero (C) It is a scalar with no direction

(D) It depends only on gravity Correct Answer: (A) Explanation: torque

is maximum when m is perpendicular to B.

Q106. Choose the correct expression or result associated with torque on

magnetic dipole. (A) τ = mB sin θ (B) The reciprocal of the stated

quantity (C) The square of the stated quantity (D) No relation can be

stated Correct Answer: (A) Explanation: torque is maximum when m is

perpendicular to B.

Q107. Which option should a student remember about torque on magnetic

dipole? (A) τ = mB sin θ (B) It contradicts the chapter’s stated rule

(C) It is independent of all physical quantities (D) It applies only

when current is zero Correct Answer: (A) Explanation: torque is maximum

when m is perpendicular to B.

Q108. Which choice is consistent with the NCERT chapter’s treatment of

torque on magnetic dipole? (A) τ = mB sin θ (B) It has the opposite

direction or dependence (C) It is unrelated to magnetic phenomena (D) It

is never used in calculations Correct Answer: (A) Explanation: torque is

maximum when m is perpendicular to B.

Q109. Which statement correctly describes stable loop equilibrium? (A)

magnetic moment parallel to B (B) It is always zero (C) It is a scalar

with no direction (D) It depends only on gravity Correct Answer: (A)

Explanation: parallel alignment is stable equilibrium.

Q110. A 0.20 kg wire of length 1.5 m carries 2 A and is suspended by a

magnetic field. What field balances its weight? (A) 0.065 T (B) 0.65 T

(C) 6.5 T (D) 65 T Correct Answer: (B) Explanation:

B=mg/(Iℓ)=(0.20×9.8)/(2×1.5)≈0.65 T.

Q111. An electron has m=9×10⁻³¹ kg, v=3×10⁷ m/s, B=6×10⁻⁴ T and

|e|=1.6×10⁻¹⁹ C. Its orbit radius is about: (A) 2.8 cm (B) 28 cm (C) 2.8

m (D) 0.28 mm Correct Answer: (B) Explanation: r=mv/(|e|B)≈0.28 m.

Q112. A 100-turn coil of radius 0.1 m carries 1 A. Its centre field is

about: (A) 6.28×10⁻⁴ T (B) 6.28×10⁻⁵ T (C) 6.28×10⁻⁶ T (D) 6.28 T

Correct Answer: (A) Explanation: B=μ₀NI/(2R)=2π×10⁻⁴ T.

Q113. A 0.5 m solenoid has 500 turns and carries 5 A. Its field is

about: (A) 6.28×10⁻³ T (B) 6.28×10⁻⁵ T (C) 6.28×10⁻¹ T (D) 6.28 T

Correct Answer: (A) Explanation: n=500/0.5=1000 m⁻¹; B=μ₀nI≈6.28×10⁻³ T.

Q114. A loop has magnetic moment 10 A m² in a 2 T field and is

perpendicular to the field. Torque is: (A) 5 N m (B) 10 N m (C) 20 N m

(D) 40 N m Correct Answer: (C) Explanation: τ=mB=10×2=20 N m.

Q115. For I=10 A, dl=1 cm, r=0.5 m and θ=90°, the Biot–Savart field

contribution is: (A) 4×10⁻⁸ T (B) 4×10⁻⁶ T (C) 4×10⁻⁴ T (D) 4 T Correct

Answer: (A) Explanation: dB=10⁻⁷ I dl/r²=4×10⁻⁸ T.

Q116. A 3 V source is in series with 60 Ω and 3 Ω. The current is

approximately: (A) 1.00 A (B) 0.99 A (C) 0.048 A (D) 3.00 A Correct

Answer: (C) Explanation: I=V/R=3/(60+3)≈0.048 A.

Q117. If the distance from a long straight wire triples, its magnetic

field becomes: (A) 3B (B) B/3 (C) B/9 (D) 9B Correct Answer: (B)

Explanation: B is inversely proportional to distance.

Q118. If current in a fixed circular coil doubles, its centre field: (A)

Halves (B) Doubles (C) Quadruples (D) Stays unchanged Correct Answer:

(B) Explanation: B=μ₀NI/(2R) is proportional to I.

Q119. If current in a long solenoid doubles while n stays fixed, its

internal field: (A) Halves (B) Doubles (C) Quadruples (D) Becomes zero

Correct Answer: (B) Explanation: B=μ₀nI.

ANSWER KEY

Q1 — A Q2 — A Q3 — A Q4 — A Q5 — A Q6 — A Q7 — A Q8 — A Q9 — A Q10 — A

Q11 — A Q12 — A Q13 — A Q14 — A Q15 — A Q16 — A Q17 — A Q18 — A Q19 — A

Q20 — A Q21 — A Q22 — A Q23 — A Q24 — A Q25 — A Q26 — A Q27 — A Q28 — A

Q29 — A Q30 — A Q31 — A Q32 — A Q33 — A Q34 — A Q35 — A Q36 — A Q37 — A

Q38 — A Q39 — A Q40 — A Q41 — A Q42 — A Q43 — A Q44 — A Q45 — A Q46 — A

Q47 — A Q48 — A Q49 — A Q50 — A Q51 — A Q52 — A Q53 — A Q54 — A Q55 — A

Q56 — A Q57 — A Q58 — A Q59 — A Q60 — A Q61 — A Q62 — A Q63 — A Q64 — A

Q65 — A Q66 — A Q67 — A Q68 — A Q69 — A Q70 — A Q71 — A Q72 — A Q73 — A

Q74 — A Q75 — A Q76 — A Q77 — A Q78 — A Q79 — A Q80 — A Q81 — A Q82 — A

Q83 — A Q84 — A Q85 — A Q86 — A Q87 — A Q88 — A Q89 — A Q90 — A Q91 — A

Q92 — A Q93 — A Q94 — A Q95 — A Q96 — A Q97 — A Q98 — A Q99 — A Q100 — A

Q101 — A Q102 — A Q103 — A Q104 — A Q105 — A Q106 — A Q107 — A Q108 — A

Q109 — A Q110 — B Q111 — B Q112 — A Q113 — A Q114 — C Q115 — A Q116 — C

Q117 — B Q118 — B Q119 — B

IMPORTANT FORMULAS FROM THE CHAPTER 1. Lorentz force: F = q(E + v × B)

2. Magnetic force magnitude: F = |q|vB sin θ 3. Force on straight

conductor: F = Iℓ × B 4. Biot–Savart law: dB = (μ₀/4π) I(dℓ × r)/r³ 5.

Biot–Savart magnitude: dB = (μ₀/4π)(I dl sin θ/r²) 6. Circular orbit

radius: r = mv/(|q|B) 7. Cyclotron angular frequency: ω = |q|B/m;

frequency ν = |q|B/(2πm) 8. Helical pitch: p = v∥T 9. Circular-loop

axial field: B = μ₀IR²/[2(x² + R²)³ᐟ²] 10. Centre field of N-turn coil:

B = μ₀NI/(2R) 11. Ampere’s law: ∮B·dℓ = μ₀I_enclosed 12. Long straight

wire: B = μ₀I/(2πr) 13. Inside uniform wire (r<a): B = μ₀Ir/(2πa²) 14.

Long solenoid: B = μ₀nI 15. Magnetic moment: m = NIA 16. Torque: τ = mB

sin θ 17. Galvanometer equilibrium: kφ = NIAB; current sensitivity φ/I =

NAB/k

KEY CONCEPTS FOR REVISION Magnetic fields are vectors and obey

superposition. Magnetic force is perpendicular to v and B and does no

work. Perpendicular motion in uniform B is circular; a parallel

component produces a helix. Biot–Savart law gives field due to a current

element. Ampere’s law is convenient for symmetric current distributions.

Long-wire field varies as 1/r; inside a uniform wire it varies as r. A

long solenoid has approximately uniform internal field. Parallel

currents attract and antiparallel currents repel. A current loop behaves

like a magnetic dipole. A galvanometer is converted into an ammeter

using a small parallel shunt and into a voltmeter using a large series

resistance.

COMMON MISTAKES TO AVOID 1. Do not confuse qE with q(v×B). 2. Magnetic

force is zero for a stationary charge or v parallel/antiparallel to B.

3. A magnetic field alone does not change speed. 4. Use |q| for

magnitudes and charge sign for direction. 5. Include sinθ and r² in

Biot–Savart magnitude. 6. Use enclosed current in Ampere’s law. 7. In

B=μ₀nI, n is turns per unit length. 8. Same-direction parallel currents

attract; opposite-direction currents repel. 9. Torque is maximum at 90°

and zero at 0° or 180°. 10. Ammeter: series and low resistance;

voltmeter: parallel and high resistance.

SOURCE NOTE Prepared from the attached NCERT Class 12 Physics chapter

“Moving Charges and Magnetism” (29 pages, Reprint 2026–27). This is a

question-bank draft based on chapter concepts and equations; review

diagram-specific questions against the original figures before

publication.