{"id":12694,"date":"2025-09-20T12:24:57","date_gmt":"2025-09-20T11:24:57","guid":{"rendered":"https:\/\/mcqsadda.com\/?p=12694"},"modified":"2025-10-22T10:09:22","modified_gmt":"2025-10-22T09:09:22","slug":"magnetic-effect-of-electric-current-top-100-mcqs-with-answer-and-explanation","status":"publish","type":"post","link":"https:\/\/mcqsadda.com\/index.php\/2025\/09\/20\/magnetic-effect-of-electric-current-top-100-mcqs-with-answer-and-explanation\/","title":{"rendered":"Magnetic effect of electric current Top 100 MCQs With Answer and Explanation"},"content":{"rendered":"\n

1. A magnetic field is produced by:<\/mark><\/strong>
A) Electric charges at rest
B) Moving electric charges
C) Gravitational forces
D) Heat energy
Answer:<\/strong> B) Moving electric charges
Explanation:<\/strong> Magnetic fields arise from motion of charges (current) or changing electric fields.<\/p>\n\n\n\n

2. The SI unit of magnetic field (magnetic flux density, B) is:
<\/strong><\/mark>A) Tesla (T)
B) Weber (Wb)
C) Ampere (A)
D) Gauss
Answer<\/strong>: A) Tesla (T)
Explanation<\/strong>: 1 T = 1 N\/(A\u00b7m).<\/p>\n\n\n\n

3. The direction of the magnetic field around a straight current-carrying wire is given by:
<\/mark><\/strong>A) Fleming\u2019s left-hand rule
B) Right-hand thumb rule
C) Ampere\u2019s law
D) Coulomb\u2019s law
Answer<\/strong>: B) Right-hand thumb rule
Explanation<\/strong>: Thumb points along current, fingers curl along magnetic field direction.<\/p>\n\n\n\n

4. Magnetic field lines:
<\/mark><\/strong>A) Start from south pole and end at north pole
B) Start from north pole and end at south pole
C) Are straight only
D) Are imaginary and random
Answer<\/strong>: B) Start from north pole and end at south pole
Explanation<\/strong>: Magnetic field lines always form closed loops outside and inside the magnet.<\/p>\n\n\n\n

5. The strength of magnetic field around a long straight wire at distance r is:
<\/mark><\/strong>A) B=\u03bc_0 I\/2\u03c0r
B) B=\u03bc_0 I\/4\u03c0r^2
C) B=\u03bc_0 I\/r
D) B=I\/r^2
Answer<\/strong>: A) B=\u03bc_0 I\/2\u03c0r
Explanation<\/strong>: Biot\u2013Savart law for a long straight wire.<\/p>\n\n\n\n

6. Unit of magnetic flux (\u03a6) is:
<\/mark><\/strong>A) Tesla (T)
B) Weber (Wb)
C) Ampere (A)
D) Henry (H)
Answer<\/strong>: B) Weber (Wb)
Explanation<\/strong>: Magnetic flux = B\u00b7A, unit is Wb.<\/p>\n\n\n\n

7. Fleming\u2019s left-hand rule is used to find:
<\/mark><\/strong>A) Direction of induced current
B) Force on current-carrying conductor in magnetic field
C) Magnetic field around wire
D) Electric field direction
Answer<\/strong>: B) Force on current-carrying conductor in magnetic field
Explanation<\/strong>: Thumb = force, forefinger = field, middle finger = current.<\/p>\n\n\n\n

8. Magnitude of magnetic force on a charge q moving with velocity v in magnetic field B at angle \u03b8 is:
<\/mark><\/strong>A) F=qvB
B) F=qvBsin\u2061\u03b8
C) F=qvBcos\u2061\u03b8
D) F=qv^2 B
Answer<\/strong>: B) F=qvBsin\u2061\u03b8
Explanation<\/strong>: Force is maximum when velocity is perpendicular to field.<\/p>\n\n\n\n

9. A charge moving parallel to magnetic field experiences:
<\/mark><\/strong>A) Maximum force
B) Zero force
C) Half force
D) Depends on speed
Answer<\/strong>: B) Zero force
Explanation<\/strong>: F = qvB sin \u03b8 \u2192 \u03b8 = 0\u00b0 \u2192 F = 0.<\/p>\n\n\n\n

10. Unit of magnetic moment (\u03bc) is:
<\/mark><\/strong>A) A\u00b7m\u00b2
B) N\u00b7m
C) Tesla
D) Weber
Answer<\/strong>: A) A\u00b7m\u00b2
Explanation<\/strong>: \u03bc = I\u00b7A, current \u00d7 area.<\/p>\n\n\n\n

11. Torque on a current-carrying loop in uniform magnetic field is:
<\/mark><\/strong>A) \u03c4 = B I A sin \u03b8
B) \u03c4 = B I A cos \u03b8
C) \u03c4 = B I A
D) \u03c4 = 0
Answer<\/strong>: A) \u03c4 = B I A sin \u03b8
Explanation<\/strong>: \u03b8 = angle between plane of loop and field.<\/p>\n\n\n\n

12. A compass needle aligns along:
<\/mark><\/strong>A) Electric field
B) Magnetic field
C) Current direction
D) Gravity
Answer<\/strong>: B) Magnetic field
Explanation<\/strong>: Needle aligns along local magnetic field lines.<\/p>\n\n\n\n

13. A solenoid behaves like:
<\/mark><\/strong>A) Permanent magnet
B) Electromagnet
C) Capacitor
D) Resistor
Answer<\/strong>: B) Electromagnet
Explanation<\/strong>: Current through coil produces magnetic field similar to bar magnet.<\/p>\n\n\n\n

14. Magnetic field at the center of a circular current loop of radius R is:
<\/mark><\/strong>A) B=\u03bc_0 I\/2R
B) B=\u03bc_0 I\/2\u03c0R
C) B=\u03bc_0 I\/4\u03c0R^2
D) B=\u03bc_0 I\/R^2
Answer<\/strong>: A) B=\u03bc_0 I\/2R
Explanation<\/strong>: From Biot\u2013Savart law for a circular loop.<\/p>\n\n\n\n

15. Magnetic lines of force are:
<\/mark><\/strong>A) Closed curves
B) Open curves
C) Straight only
D) Random
Answer<\/strong>: A) Closed curves
Explanation<\/strong>: They start from N pole and end at S pole outside magnet, forming loops inside.<\/p>\n\n\n\n

16. Magnetic field inside a long solenoid of n turns\/m and current I is:
<\/mark><\/strong>A) B = \u03bc\u2080 n I
B) B = \u03bc\u2080 I \/ 2\u03c0 r
C) B = \u03bc\u2080 I n\u00b2
D) B = \u03bc\u2080 I \/ L
Answer<\/strong>: A) B = \u03bc\u2080 n I
Explanation<\/strong>: Field inside solenoid is uniform.<\/p>\n\n\n\n

17. Direction of magnetic field inside solenoid is determined by:
<\/mark><\/strong>A) Fleming\u2019s left-hand rule
B) Right-hand screw rule
C) Biot\u2013Savart law
D) Coulomb\u2019s law
Answer<\/strong>: B) Right-hand screw rule
Explanation<\/strong>: Curl fingers along current, thumb gives field direction.<\/p>\n\n\n\n

18. Two parallel wires carrying current in same direction:
<\/mark><\/strong>A) Repel
B) Attract
C) No force
D) Depends on current
Answer<\/strong>: B) Attract
Explanation<\/strong>: Magnetic field produced by each wire exerts force on the other.<\/p>\n\n\n\n

19. Two parallel wires carrying current in opposite direction:
<\/mark><\/strong>A) Attract
B) Repel
C) Neutral
D) None
Answer<\/strong>: B) Repel
Explanation<\/strong>: Currents in opposite direction produce opposing fields \u2192 repulsion.<\/p>\n\n\n\n

20. Ampere\u2019s force between two parallel wires:
<\/mark><\/strong>A) F\/L=(\u03bc_0 I_1 I_2)\/2\u03c0d
B) F\/L=(\u03bc_0 I_1 I_2)\/d^2
C) F\/L=\u03bc_0 I_1 I_2
D) F = 0
Answer<\/strong>: A) F\/L=(\u03bc_0 I_1 I_2)\/2\u03c0d
Explanation<\/strong>: Standard formula for force per unit length.<\/p>\n\n\n\n

21. Magnetic field at point due to infinite straight wire decreases with:
<\/mark><\/strong>A) 1\/r
B) 1\/r\u00b2
C) r\u00b2
D) r
Answer<\/strong>: A) 1\/r
Explanation<\/strong>: Biot\u2013Savart law for straight wire: B \u221d 1\/r.<\/p>\n\n\n\n

22. SI unit of magnetic dipole moment:
<\/mark><\/strong>A) A\u00b7m\u00b2
B) N\u00b7m
C) J\/T
D) Both A & C
Answer<\/strong>: D) Both A & C
Explanation<\/strong>: \u03bc = I\u00b7A = torque\/field, both units equivalent.<\/p>\n\n\n\n

23. A charge moving in a magnetic field in circular path has:
<\/mark><\/strong>A) Constant speed
B) Zero acceleration
C) Zero force
D) Increasing speed
Answer<\/strong>: A) Constant speed
Explanation<\/strong>: Magnetic force is perpendicular to velocity \u2192 centripetal motion, speed constant.<\/p>\n\n\n\n

24. Radius of circular path of charge q, mass m, velocity v in perpendicular B:
<\/mark><\/strong>A) r = mv\/qB
B) r = qB\/mv
C) r = mv\u00b2\/qB
D) r = qBv\/m
Answer<\/strong>: A) r = mv\/qB
Explanation<\/strong>: Centripetal force mv\u00b2\/r = qvB \u2192 r = mv\/qB.<\/p>\n\n\n\n

25. Time period of circular motion of charge in uniform magnetic field:
<\/mark><\/strong>A) T=2\u03c0m\/qB
B) T=2\u03c0q\/mB
C) T=2\u03c0m\/q
D) T=q\/mB
Answer<\/strong>: A) T=2\u03c0m\/qB
Explanation:<\/strong> T = 2\u03c0r\/v = 2\u03c0 m\/qB.
<\/p>\n\n\n\n

26. The magnetic field at a point due to a small current element I”\u2009” dlis given by:
<\/mark><\/strong>A) Ampere\u2019s law
B) Biot\u2013Savart law
C) Faraday\u2019s law
D) Coulomb\u2019s law
Answer<\/strong>: B) Biot\u2013Savart law
Explanation:<\/strong> Biot\u2013Savart law relates a small current element to the magnetic field it produces at a point.<\/p>\n\n\n\n

27. Magnetic field due to a small current element Idlat distance r is:
<\/mark><\/strong>A) dB\u221dIdl\/r
B) dB\u221dIdl\/r^2
C) dB\u221dIdl\/r^3
D) dB\u221dIdl
Answer:<\/strong> B) dB\u221dIdl\/r^2
Explanation<\/strong>: Biot\u2013Savart law: dB \u20d7=(\u03bc_0\/4\u03c0)(I”\u2009” dl \u20d7\u00d7r \u0302)\/r^2.<\/p>\n\n\n\n

28. Direction of magnetic field due to current element is:
<\/mark><\/strong>A) Along current
B) Along radius
C) Perpendicular to plane of current element and radius vector
D) Opposite to current
Answer<\/strong>: C) Perpendicular to plane of current element and radius vector
Explanation<\/strong>: Cross product in Biot\u2013Savart law gives direction.<\/p>\n\n\n\n

29. Magnetic field at center of circular loop of radius R carrying current I:
<\/mark><\/strong>A) B=\u03bc_0 I\/2\u03c0R
B) B=\u03bc_0 I\/2R
C) B=\u03bc_0 I\/4\u03c0R^2
D) B=\u03bc_0 I\/R^2
Answer:<\/strong> B) B=\u03bc_0 I\/2R
Explanation:<\/strong> Biot\u2013Savart integration over circular loop.<\/p>\n\n\n\n

30. Field at the center of a semicircular wire of radius R carrying current I:
<\/mark><\/strong>A) B=\u03bc_0 I\/4R
B) B=\u03bc_0 I\/2R
C) B=\u03bc_0 I\/4\u03c0R
D) B=\u03bc_0 I\/8R
Answer:<\/strong> A) B=\u03bc_0 I\/4R
Explanation<\/strong>: B = (\u03bc\u2080 I \/ 4R) for semicircle (half of full circle).<\/p>\n\n\n\n

31. Magnetic field at the axis of a solenoid (length L >> radius) with n turns\/m and current I:
<\/mark><\/strong>A) B=\u03bc_0 nI
B) B=\u03bc_0 I\/2R
C) B=\u03bc_0 In^2
D) B=\u03bc_0 IL
Answer<\/strong>: A) B=\u03bc_0 nI
Explanation<\/strong>: Field inside long solenoid uniform.<\/p>\n\n\n\n

32. Magnetic field inside a toroid of mean radius R and N turns carrying current I:
<\/mark><\/strong>A) B=\u03bc_0 NI\/2\u03c0R
B) B=\u03bc_0 NI\/R
C) B=\u03bc_0 I\/2R
D) B=\u03bc_0 I\/2\u03c0R^2
Answer<\/strong>: A) B=\u03bc_0 NI\/2\u03c0R
Explanation<\/strong>: Field confined inside toroid, derived via Ampere\u2019s law.<\/p>\n\n\n\n

33. Ampere\u2019s circuital law states:
<\/mark><\/strong>A) Magnetic field along path = \u03bc\u2080 \u00d7 total current enclosed
B) \u222eB \u20d7\u22c5dl \u20d7=\u03bc_0 I_enclosed
C) Magnetic field due to charges only
D) Both A & B
Answer<\/strong>: D) Both A & B
Explanation<\/strong>: Ampere\u2019s law relates line integral of B to current enclosed.<\/p>\n\n\n\n

34. For a straight wire, Ampere\u2019s law gives:
<\/mark><\/strong>A) B=\u03bc_0 I\/2\u03c0r
B) B=\u03bc_0 I\/2R
C) B=\u03bc_0 I\/R^2
D) B=\u03bc_0 I\/4\u03c0R^2
Answer<\/strong>: A) B=\u03bc_0 I\/2\u03c0r
Explanation<\/strong>: Same as Biot\u2013Savart for long straight wire.<\/p>\n\n\n\n

35. Magnetic field inside an ideal solenoid is:
<\/mark><\/strong>A) Non-uniform
B) Uniform and along axis
C) Zero
D) Radial
Answer<\/strong>: B) Uniform and along axis
Explanation<\/strong>: Superposition of fields from all turns produces uniform field.<\/p>\n\n\n\n

36. For circular current loop, magnetic moment \u03bc =
<\/mark><\/strong>A) I \u00d7 circumference
B) I \u00d7 area of loop
C) B \u00d7 area
D) I\u00b2 \u00d7 area
Answer<\/strong>: B) I \u00d7 area of loop
Explanation<\/strong>: \u03bc = I\u00b7A, defines strength of current loop.<\/p>\n\n\n\n

37. Unit of magnetic moment in SI:
<\/mark><\/strong>A) Tesla
B) Ampere\u00b7m\u00b2
C) Weber
D) Henry
Answer: <\/strong>B) Ampere\u00b7m\u00b2
Explanation<\/strong>: \u03bc = I \u00d7 A \u2192 unit A\u00b7m\u00b2.<\/p>\n\n\n\n

38. Torque on current-carrying loop in uniform B field:
<\/mark><\/strong>A) \u03c4 = \u03bc B sin \u03b8
B) \u03c4 = \u03bc B cos \u03b8
C) \u03c4 = \u03bc B
D) \u03c4 = 0
Answer<\/strong>: A) \u03c4 = \u03bc B sin \u03b8
Explanation:<\/strong> \u03b8 = angle between \u03bc and B.<\/p>\n\n\n\n

39. Potential energy of magnetic dipole in magnetic field:
<\/mark><\/strong>A) U = \u2013 \u03bc \u00b7 B
B) U = \u03bc \u00b7 B
C) U = \u03bc \/ B
D) U = 0
Answer<\/strong>: A) U = \u2013 \u03bc \u00b7 B
Explanation<\/strong>: Minimum energy when \u03bc aligns with B.<\/p>\n\n\n\n

40. Right-hand screw rule determines:
<\/mark><\/strong>A) Current direction from B
B) B direction around current
C) Force on conductor
D) Magnetic flux
Answer<\/strong>: B) B direction around current
Explanation<\/strong>: Curl fingers along rotation, thumb shows current.<\/p>\n\n\n\n

41. Two parallel wires carrying currents in same direction experience:
<\/mark><\/strong>A) Repulsion
B) Attraction
C) No force
D) Varies with distance
Answer<\/strong>: B) Attraction
Explanation<\/strong>: Like currents attract; basis of defining ampere.<\/p>\n\n\n\n

42. Unit force per unit length between parallel wires:
<\/mark><\/strong>A) 2\u00d710\u207b\u2077 N\/m per 1 A current separated by 1 m
B) 10\u207b\u2077 N\/m
C) 1 N\/m
D) 10\u207b\u00b3 N\/m
Answer<\/strong>: A) 2\u00d710\u207b\u2077 N\/m per 1 A current separated by 1 m
Explanation<\/strong>: Defines 1 Ampere.<\/p>\n\n\n\n

43. Magnetic field at distance r from infinite wire decreases as:
<\/mark><\/strong>A) 1\/r\u00b2
B) 1\/r
C) r\u00b2
D) r
Answer<\/strong>: B) 1\/r
Explanation<\/strong>: Biot\u2013Savart law: B \u221d 1\/r.<\/p>\n\n\n\n

44. Magnetic field outside a very long solenoid is:
<\/mark><\/strong>A) Uniform
B) Zero
C) Maximum
D) Same as inside
Answer<\/strong>: B) Zero
Explanation<\/strong>: Fields from turns cancel outside.<\/p>\n\n\n\n

45. Magnetic field inside toroid:
<\/mark><\/strong>A) Uniform along circular path
B) Radial
C) Zero
D) Tangential but varying
Answer<\/strong>: A) Uniform along circular path
Explanation<\/strong>: Symmetry \u2192 B constant along each circular loop.
<\/p>\n\n\n\n

46. A current-carrying loop produces field:
<\/mark><\/strong>A) Only at center
B) Along axis
C) Uniform everywhere
D) None
Answer<\/strong>: B) Along axis
Explanation<\/strong>: B strongest at center, decreases along axis.<\/p>\n\n\n\n

47. Magnetic field at axis of circular coil of N turns:
<\/mark><\/strong>A) B=\u03bc_0 NI\/2R
B) B=\u03bc_0 I\/2R
C) B=\u03bc_0 I\/R
D) B=\u03bc_0 NI\/R
Answer<\/strong>: A) B=\u03bc_0 NI\/2R
Explanation<\/strong>: Multiply single loop field by N turns.<\/p>\n\n\n\n

48. Magnetic field at point on axis of short solenoid:
<\/mark><\/strong>A) Uniform
B) Non-uniform
C) Zero
D) Radial
Answer<\/strong>: B) Non-uniform
Explanation<\/strong>: Only long solenoid approximates uniform field.<\/p>\n\n\n\n

49. For long straight wire, magnetic field at 1 m from 1 A current:
<\/mark><\/strong>A) 2\u00d710^(-7) T
B) 10^(-7) T
C) 4\u00d710^(-7) T
D) 8\u00d710^(-7) T
Answer<\/strong>: A) 2\u00d710^(-7) T
Explanation<\/strong>: B = \u03bc\u2080 I \/ 2\u03c0r \u2192 \u03bc\u2080 = 4\u03c0\u00d710\u207b\u2077.<\/p>\n\n\n\n

50. Magnetic field of coil increases by:
<\/mark><\/strong>A) Increasing current
B) Increasing number of turns
C) Reducing coil radius
D) All of above
Answer<\/strong>: D) All of above
Explanation<\/strong>: B \u221d N I \/ R.
<\/p>\n\n\n\n

51. Electromagnetic induction is the phenomenon of:<\/strong>
<\/mark>A) Generation of magnetic field by current
B) Induction of current in a conductor due to changing magnetic field
C) Attraction between magnets
D) Magnetic field due to moving charges
Answer<\/strong>: B) Induction of current in a conductor due to changing magnetic field
Explanation<\/strong>: Faraday\u2019s experiments showed changing flux induces current.<\/p>\n\n\n\n

52. Faraday\u2019s law states:
<\/mark><\/strong>A) Induced emf \u221d magnetic field
B) Induced emf \u221d rate of change of magnetic flux
C) Induced emf \u221d current
D) Induced emf \u221d resistance
Answer<\/strong>: B) Induced emf \u221d rate of change of magnetic flux
Explanation<\/strong>: E=-d\u03a6_B\/dt<\/p>\n\n\n\n

53. Lenz\u2019s law gives:
<\/mark><\/strong>A) Direction of induced current
B) Magnitude of induced current
C) Both direction and magnitude
D) None
Answer<\/strong>: A) Direction of induced current
Explanation<\/strong>: Induced current opposes change in flux (conservation of energy).<\/p>\n\n\n\n

54. Unit of magnetic flux (\u03a6) is:
<\/mark><\/strong>A) Tesla
B) Weber
C) Ampere\u00b7turn
D) Henry
Answer<\/strong>: B) Weber (Wb)
Explanation<\/strong>: Flux = B\u00b7A, 1 Wb = 1 T\u00b7m\u00b2.<\/p>\n\n\n\n

55. Unit of induced emf is:
<\/mark><\/strong>A) Tesla
B) Volt
C) Weber
D) Ampere
Answer<\/strong>: B) Volt
Explanation<\/strong>: EMF is potential difference induced.<\/p>\n\n\n\n

56. A conductor moving in uniform magnetic field experiences:
<\/mark><\/strong>A) Constant magnetic flux
B) Induced emf
C) Zero current
D) Zero voltage
Answer<\/strong>: B) Induced emf
Explanation<\/strong>: Motion changes flux through conductor \u2192 Faraday\u2019s law.<\/p>\n\n\n\n

57. Induced emf in a coil rotating in uniform B-field is maximum when:
<\/mark><\/strong>A) Plane of coil parallel to field
B) Plane of coil perpendicular to field
C) Coil stationary
D) Coil axis perpendicular to field
Answer<\/strong>: B) Plane of coil perpendicular to field
Explanation<\/strong>: Flux changes fastest \u2192 max emf.<\/p>\n\n\n\n

58. Induced emf in coil:
<\/mark><\/strong>A) Zero if flux constant
B) Max if flux changes fastest
C) Always constant
D) Depends on coil material
Answer<\/strong>: A) Zero if flux constant
Explanation<\/strong>: No change in flux \u2192 no induced emf.<\/p>\n\n\n\n

59. EMF induced in a coil of N turns:
<\/mark><\/strong>A) E=Nd\u03a6\/dt
B) E=d\u03a6\/dt
C) E=N\u03a6
D) E=NI
Answer<\/strong>: A) E=Nd\u03a6\/dt
Explanation<\/strong>: Faraday\u2019s law generalized for N turns.<\/p>\n\n\n\n

60. A bar magnet moving toward a coil induces:
<\/mark><\/strong>A) Current in same direction as flux change
B) Current opposing flux change
C) Zero current
D) Infinite current
Answer<\/strong>: B) Current opposing flux change
Explanation<\/strong>: Lenz\u2019s law ensures induced current opposes motion.<\/p>\n\n\n\n

61. Magnetic flux through coil of area A in uniform B:
<\/mark><\/strong>A) \u03a6=B\/A
B) \u03a6=B\u22c5Acos\u2061\u03b8
C) \u03a6=B+A
D) \u03a6=BA\/\u03b8
Answer<\/strong>: B) \u03a6=B\u22c5Acos\u2061\u03b8
Explanation<\/strong>: \u03b8 = angle between B and normal to plane of coil.<\/p>\n\n\n\n

62. Motional emf is generated due to:
<\/mark><\/strong>A) Changing B-field
B) Motion of conductor in B-field
C) Resistance
D) Temperature
Answer<\/strong>: B) Motion of conductor in B-field
Explanation<\/strong>: Conductor cuts magnetic lines \u2192 induced emf.<\/p>\n\n\n\n

63. EMF induced in rod of length l moving with velocity v perpendicular to B:
<\/mark><\/strong>A) E=Blv
B) E=Bl\/v
C) E=Blv^2
D) E=B\/lv
Answer<\/strong>: A) E=Blv
Explanation<\/strong>: Motional emf formula: \u03b5 = B l v.<\/p>\n\n\n\n

64. Eddy currents are induced in:
<\/mark><\/strong>A) Insulators
B) Conductors
C) Non-conductors
D) Vacuum
Answer<\/strong>: B) Conductors
Explanation<\/strong>: Loop currents induced in bulk of conducting material.<\/p>\n\n\n\n

65. Lenz\u2019s law ensures:
<\/mark><\/strong>A) Energy conservation
B) Maximum current
C) Minimum resistance
D) None
Answer<\/strong>: A) Energy conservation
Explanation<\/strong>: Induced current always opposes change \u2192 work done = energy.<\/p>\n\n\n\n

66. Direction of induced current in moving magnet-coil system given by:
<\/mark><\/strong>A) Right-hand rule
B) Left-hand rule
C) Fleming\u2019s right-hand rule
D) Fleming\u2019s left-hand rule
Answer<\/strong>: C) Fleming\u2019s right-hand rule
Explanation<\/strong>: Right-hand rule for generators \u2192 direction of induced current.<\/p>\n\n\n\n

67. Changing area of loop in uniform B produces:
<\/mark><\/strong>A) No EMF
B) Induced EMF
C) Only flux
D) Only torque
Answer<\/strong>: B) Induced EMF
Explanation<\/strong>: Change in flux (B\u00b7A) \u2192 EMF induced.<\/p>\n\n\n\n

68. Self-induction occurs due to:
<\/mark><\/strong>A) Mutual induction
B) Changing current in same coil
C) Static magnetic field
D) Electrostatics
Answer:<\/strong> B) Changing current in same coil
Explanation<\/strong>: Time-varying current induces EMF in same coil \u2192 Lenz\u2019s law.<\/p>\n\n\n\n

69. Inductance unit:<\/mark><\/strong>
A) Weber
B) Henry
C) Tesla
D) Volt
Answe<\/strong>r: B) Henry (H)
Explanation:<\/strong> L = EMF \/ (dI\/dt).
<\/p>\n\n\n\n

70. Mutual induction occurs when:
<\/mark><\/strong>A) EMF induced in one coil due to current change in another coil
B) EMF induced in same coil
C) Magnetic field is uniform
D) Current constant
Answer:<\/strong> A) EMF induced in one coil due to current change in another coil
Explanation<\/strong>: Basis for transformers.<\/p>\n\n\n\n

71. Transformer works on principle of:
<\/mark><\/strong>A) Self-induction only
B) Mutual induction
C) Static electricity
D) Magnetic monopoles
Answer<\/strong>: B) Mutual induction
Explanation<\/strong>: Changing current in primary \u2192 changing flux \u2192 induces EMF in secondary.<\/p>\n\n\n\n

72. Induced EMF in secondary coil:
<\/mark><\/strong>A) Directly proportional to turns of secondary
B) Inversely proportional to primary turns
C) Independent of turns
D) Zero
Answer<\/strong>: A) Directly proportional to turns of secondary
Explanation<\/strong>: Faraday\u2019s law: \u03b5 \u221d N d\u03a6\/dt.<\/p>\n\n\n\n

73. Energy stored in inductor L carrying current I:
<\/mark><\/strong>A) U=1\/2 LI^2
B) U=LI
C) U=1\/2 I^2\/L
D) U=I\/L
Answer<\/strong>: A) U=1\/2 LI^2
Explanation<\/strong>: Energy stored in magnetic field of inductor.<\/p>\n\n\n\n

74. Back EMF in motor opposes:
<\/mark><\/strong>A) Applied voltage
B) Magnetic field
C) Current flow
D) Resistance
Answer<\/strong>: C) Current flow
Explanation<\/strong>: Lenz\u2019s law: induced EMF opposes cause (current) in coil.<\/p>\n\n\n\n

75. EMF induced is maximum when:
<\/mark><\/strong>A) Magnetic flux changes fastest
B) Flux constant
C) Coil stationary
D) Coil parallel to field
Answer<\/strong>: A) Magnetic flux changes fastest
Explanation<\/strong>: Rate of change of flux determines EMF magnitude.
<\/p>\n\n\n\n

76. The device which converts electrical energy into mechanical energy is:
<\/mark><\/strong>A) Generator
B) Motor
C) Transformer
D) Dynamo
Answer<\/strong>: B) Motor
Explanation<\/strong>: Electric motor works on principle of force on current-carrying conductor in magnetic field.<\/p>\n\n\n\n

77. The device which converts mechanical energy into electrical energy is:
<\/mark><\/strong>A) Motor
B) Generator
C) Transformer
D) Battery
Answer<\/strong>: B) Generator
Explanation<\/strong>: Electromagnetic induction principle: rotating coil in B-field produces EMF.<\/p>\n\n\n\n

78. The principle of DC motor is:
<\/mark><\/strong>A) Electromagnetic induction
B) Force on current-carrying conductor in magnetic field
C) Mutual induction
D) Self-induction
Answer<\/strong>: B) Force on current-carrying conductor in magnetic field
Explanation<\/strong>: Torque on loop \u2192 rotation.<\/p>\n\n\n\n

79. Torque on rectangular coil in motor is maximum when plane of coil is:
<\/mark><\/strong>A) Parallel to magnetic field
B) Perpendicular to magnetic field
C) At 45\u00b0 to field
D) Any orientation
Answer<\/strong>: B) Perpendicular to magnetic field
Explanation<\/strong>: Torque \u03c4 = \u03bcB sin \u03b8 \u2192 maximum at \u03b8 = 90\u00b0.<\/p>\n\n\n\n

80. Back EMF in motor is produced due to:
<\/mark><\/strong>A) Motion of coil in magnetic field
B) Resistance of coil
C) Supply voltage
D) Magnetic flux
Answer<\/strong>: A) Motion of coil in magnetic field
Explanation<\/strong>: EMF induced opposes applied voltage, limiting current.<\/p>\n\n\n\n

81. Transformer operates on:
<\/mark><\/strong>A) DC supply
B) AC supply
C) Constant current
D) None
Answer<\/strong>: B) AC supply
Explanation<\/strong>: Only changing flux (AC) induces EMF in secondary.<\/p>\n\n\n\n

82. Step-up transformer increases:
<\/mark><\/strong>A) Current
B) Voltage
C) Resistance
D) Power
Answer<\/strong>: B) Voltage
Explanation<\/strong>: V\u2082\/V\u2081 = N\u2082\/N\u2081 \u2192 N\u2082 > N\u2081 \u2192 voltage increases.<\/p>\n\n\n\n

83. Step-down transformer decreases:
<\/mark><\/strong>A) Voltage
B) Current
C) Resistance
D) Power
Answer<\/strong>: A) Voltage
Explanation<\/strong>: N\u2082 < N\u2081 \u2192 V\u2082 < V\u2081.<\/p>\n\n\n\n

84. Efficiency of ideal transformer:
<\/mark><\/strong>A) 50%
B) 75%
C) 100%
D) 0%
Answer<\/strong>: C) 100%
Explanation<\/strong>: Ideal \u2192 negligible losses, power in = power out.<\/p>\n\n\n\n

85. Energy loss in transformer occurs due to:
<\/mark><\/strong>A) Eddy currents
B) Hysteresis
C) Resistance of coil
D) All of the above
Answer<\/strong>: D) All of the above
Explanation<\/strong>: Real transformers have losses due to these factors.<\/p>\n\n\n\n

86. Induced EMF in rotating coil of generator is maximum when plane of coil is:
<\/mark><\/strong>A) Parallel to B-field
B) Perpendicular to B-field
C) Stationary
D) At 45\u00b0
Answer<\/strong>: A) Parallel to B-field
Explanation<\/strong>: Rate of change of flux maximum when plane parallel (axis perpendicular).<\/p>\n\n\n\n

87. Frequency of AC induced in generator depends on:
<\/mark><\/strong>A) Number of turns only
B) Speed of rotation only
C) Both speed and number of poles
D) Voltage applied
Answer<\/strong>: C) Both speed and number of poles
Explanation<\/strong>: f = (np)\/120 for n rpm, p poles.<\/p>\n\n\n\n

88. In AC generator, slip rings:
<\/mark><\/strong>A) Connect coil to external circuit continuously
B) Reverse current direction
C) Act as brushes
D) None
Answer<\/strong>: A) Connect coil to external circuit continuously
Explanation<\/strong>: Allow AC output; contrast with commutator in DC.<\/p>\n\n\n\n

89. In DC generator, commutator:
<\/mark><\/strong>A) Produces AC
B) Converts AC to DC
C) Increases voltage
D) Reduces resistance
Answer<\/strong>: B) Converts AC to DC
Explanation<\/strong>: Segmented commutator reverses current direction in coil \u2192 DC output.<\/p>\n\n\n\n

90. RMS value of AC:
<\/mark><\/strong>A) Maximum value
B) Average value
C) V_rms=V_0\/\u221a2
D) Twice max value
Answer<\/strong>: C) V_rms=V_0\/\u221a2
Explanation<\/strong>: Standard relation for sinusoidal AC.<\/p>\n\n\n\n

91. Peak value of AC current I\u2080 related to RMS I:
<\/mark><\/strong>A) I_0=I_rms
B) I_0=\u221a2 I_rms
C) I_0=I_rms\/2
D) I_0=2I_rms
Answer<\/strong>: B) I_0=\u221a2 I_rms
Explanation<\/strong>: RMS is effective value: I_rms=I_0\/\u221a2.<\/p>\n\n\n\n

92. Induced EMF in rod moving in uniform B-field:
<\/mark><\/strong>A) E=Blv
B) E=B\/lv
C) E=Bv\/l
D) E=Bv^2 l
Answer<\/strong>: A) E=Blv
Explanation<\/strong>: Motional EMF formula.<\/p>\n\n\n\n

93. Induced current in short-circuited coil opposes:
<\/mark><\/strong>A) Change in flux
B) Voltage supply
C) Resistance
D) None
Answer<\/strong>: A) Change in flux
Explanation<\/strong>: Lenz\u2019s law.<\/p>\n\n\n\n

94. A loop rotating in B-field experiences torque:
<\/mark><\/strong>A) \u03c4 = \u03bcB sin \u03b8
B) \u03c4 = \u03bcB cos \u03b8
C) \u03c4 = \u03bcB
D) \u03c4 = 0
Answer<\/strong>: A) \u03c4 = \u03bcB sin \u03b8
Explanation<\/strong>: Standard torque formula for magnetic dipole.<\/p>\n\n\n\n

95. Hall effect helps measure:
<\/mark><\/strong>A) Magnetic field
B) Charge carrier density
C) Current type (electrons\/holes)
D) All of the above
Answer<\/strong>: D) All of the above
Explanation<\/strong>: Hall voltage depends on B, carrier density, and charge sign.<\/p>\n\n\n\n

96. Direction of Hall voltage determined by:
<\/mark><\/strong>A) Fleming\u2019s left-hand rule
B) Right-hand rule
C) Lenz\u2019s law
D) Biot\u2013Savart law
Answer<\/strong>: B) Right-hand rule
Explanation<\/strong>: For conventional current and magnetic field, right-hand gives sign.<\/p>\n\n\n\n

97. In magnetic braking, eddy currents:
<\/mark><\/strong>A) Slow motion of conductor
B) Accelerate motion
C) Generate power only
D) Heat nothing
Answer<\/strong>: A) Slow motion of conductor
Explanation<\/strong>: Lenz\u2019s law \u2192 currents oppose motion \u2192 braking effect.<\/p>\n\n\n\n

98. Magnetic flux linkage in coil:
<\/mark><\/strong>A) \u03a6 \u00d7 N
B) B \u00d7 A
C) \u03bc\u2080 I
D) None
Answer<\/strong>: A) \u03a6 \u00d7 N
Explanation<\/strong>: Flux through N turns \u2192 total flux linkage.<\/p>\n\n\n\n

99. Energy stored in inductor:
<\/mark><\/strong>A) U = \u00bd L I\u00b2
B) U = L I
C) U = LI\u00b2
D) U = \u00bd I\u00b2\/L
Answer<\/strong>: A) U = \u00bd L I\u00b2
Explanation<\/strong>: Magnetic energy stored in inductor field.<\/p>\n\n\n\n

100. Which of the following is NOT an application of electromagnetic induction?
<\/mark><\/strong>A) Transformer
B) AC generator
C) Electric motor
D) Electric heater
Answer<\/strong>: D) Electric heater
Explanation<\/strong>: Heater works by resistive heating, not induction.<\/p>\n","protected":false},"excerpt":{"rendered":"

1. A magnetic field is produced by:A) Electric charges at restB) Moving electric chargesC) Gravitational forcesD) Heat energyAnswer: B) Moving electric chargesExplanation: Magnetic fields arise from motion of charges (current) or changing electric fields. 2. The SI unit of magnetic field (magnetic flux density, B) is:A) Tesla (T)B) Weber (Wb)C) Ampere (A)D) GaussAnswer: A) Tesla<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[15737,15481,15857,15821,15720,15819,15859,15816,15727,15855,15736,15854,10964,15858,15729,15853,15738,4029,5649,15465,5623,15856,15536,15479,15474,15467,15483,15472,15592,15456,15478,15735,15469,15480],"class_list":{"0":"post-12694","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-physics","7":"tag-amperes-law","8":"tag-competitive-exam-physics","9":"tag-current-and-magnetism","10":"tag-electric-circuits","11":"tag-electric-current","12":"tag-electromagnet","13":"tag-electromagnetic-concepts","14":"tag-electromagnetic-induction","15":"tag-electromagnetism","16":"tag-flemings-left-hand-rule","17":"tag-lorentz-force","18":"tag-magnetic-effect-of-electric-current","19":"tag-magnetic-effect-of-electric-current-top-100-mcqs-with-answer-and-explanation","20":"tag-magnetic-effects","21":"tag-magnetic-field","22":"tag-magnetic-force-problems","23":"tag-magnetic-lines-of-force","24":"tag-mcqs-adda","25":"tag-mcqs-for-pc-psi-sda-fda-pdo-vao-banking-kas-ias-ssc-gd-ssc-chsl-ssc-cgl-for-all-compitative-exams","26":"tag-mcqs-for-physics-exam","27":"tag-mcqs-for-sda-fda-pdo-vao-banking-kas-ias-ssc-gd-ssc-chsl-ssc-cgl-for-all-compitative-exams","28":"tag-oersted-experiment","29":"tag-physics-formulas","30":"tag-physics-learning","31":"tag-physics-mcqs","32":"tag-physics-preparation-material","33":"tag-physics-questions-and-answers","34":"tag-physics-quiz","35":"tag-physics-revision","36":"tag-physics-study-material","37":"tag-psc-physics-mcqs","38":"tag-solenoid","39":"tag-ssc-physics-mcqs","40":"tag-upsc-physics-mcqs"},"_links":{"self":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12694","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/comments?post=12694"}],"version-history":[{"count":3,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12694\/revisions"}],"predecessor-version":[{"id":12725,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12694\/revisions\/12725"}],"wp:attachment":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/media?parent=12694"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/categories?post=12694"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/tags?post=12694"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}