1. The magnitude of induced emf is given by Faraday's law as:
A) \(\varepsilon = \frac{d\phi}{dt}\)
B) \(\varepsilon = -N\frac{d\phi}{dt}\)
C) \(\varepsilon = N\frac{d\phi}{dt}\)
D) \(\varepsilon = -\frac{d\phi}{Ndt}\)
2. When magnetic flux through a loop increases, the induced current will:
A) Create magnetic field opposing the increase
B) Create magnetic field aiding the increase
C"> Produce no magnetic field
D) Depends on resistance
3. The time rate of change of magnetic flux linkage gives:
A) Current
B) Induced emf
C) Resistance
D"> Magnetic field
4. A coil has resistance R and self-inductance L. The time constant τ is:
A) R/L
B) L/R
C"> RL
D) 1/RL
5. In a closed loop, the total induced emf is equal to the rate of change of:
A) Magnetic field
B) Magnetic flux
C"> Electric flux
D) Current
6. The negative sign in Faraday's law indicates:
A) Direction of induced emf
B) Magnitude of flux
C"> Loss of energy
D) Resistance effect
7. A straight conductor of length l moves with velocity v perpendicular to B. Induced emf is:
A) Blv sinθ
B) Blv
C"> Bv/l
D) Zero
8. For motional emf, the velocity must have component:
A) Parallel to B
B) Perpendicular to B and l
C"> Along the length l
D) Any direction
9. A conducting rod sliding on two parallel rails forms a closed loop. If rod moves with constant v, induced emf is:
A) Constant
B) Increasing
C"> Decreasing
D) Zero
10. Self-inductance of a coil depends on:
A) Shape and size
B) Number of turns
C"> Medium
D) All of above
11. Mutual inductance M has unit:
A) Henry
B) Weber
C"> Tesla
D) Volt
12. In a transformer, mutual inductance is maximum when coils are:
A) On same core
B) Far apart
C"> Perpendicular
D) Opposite wound
13. Eddy currents cause:
A) Energy loss as heat
B) Increase in efficiency
C"> No loss
D) Cooling effect
14. Lamination reduces eddy currents by:
A) Increasing resistance
B) Decreasing area
C"> Both A and B
D) Decreasing flux
15. In AC generator, frequency f =:
A) np/60
B) p/60n
C"> n/60p
D) np/120
16. Peak emf in AC generator E₀ =:
A) NBAω
B) NBA/ω
C"> NBω/A
D) NBAω sinωt
17. Slip rings in AC generator provide:
A) DC output
B) AC output
C"> No output
D"> Pulsating DC
18. Commutator in DC generator provides:
A) AC output
B) DC output
C"> No output
D"> Pulsating DC
19. Back emf in DC motor is:
A) E = kNφω
B) E = kNφ/ω
C"> E = kω/φ
D"> E = constant
20. Maxwell's correction to Ampere's law introduced:
A) Displacement current
B"> Conduction current
C"> Magnetic field
D"> Electric field
21. Displacement current density J_d =:
A) ε₀ dE/dt
B"> dE/dt
C"> ε₀E
D"> E/dt
22. EM waves are produced by:
A) Oscillating electric charges
B"> Steady currents
C"> Stationary charges
D"> Constant B field
23. In EM wave, E, B and propagation direction are:
A) Mutually perpendicular
B"> Parallel
C"> E || B
D"> Random
24. Speed of light c =:
A) 3×10⁸ m/s
B"> 3×10⁶ m/s
C"> 3×10¹⁰ m/s
D"> 3×10⁴ m/s
25. c = 1/√(μ₀ε₀) gives speed in:
A) Vacuum
B"> Water
C"> Glass
D"> Air only
26. The Poynting vector S points in direction of:
A) Energy flow
B"> E field
C"> B field
D"> Propagation only
27. S = (1/μ₀) E × B represents:
A) Energy flux
B"> Momentum flux
C"> Force
D"> Power
28. Average energy density of EM wave u_avg =:
A) ε₀E₀²/2
B"> ε₀E₀²
C"> B₀²/2μ₀
D"> Both A and C
29. Intensity I of EM wave is:
A) c × u_avg
B"> u_avg/c
C"> u_avg
D"> Zero
30. Radiation pressure for perfect absorption is:
A) I/c
B"> 2I/c
C"> I/c²
D"> 2Ic
31. EM spectrum arranged by decreasing wavelength:
A) γ-rays, X-rays, UV, visible, IR, microwave, radio
B"> Radio, microwave, IR, visible, UV, X-rays, γ-rays
C"> Visible, IR, UV, X-rays
D"> IR, UV, visible, X-rays
32. Radio waves have wavelength range:
A) > 10⁴ m
B"> 400-700 nm
C"> 10-100 m
D"> < 10 nm
33. Microwaves are used in:
A) Radar and cooking
B"> X-ray imaging
C"> UV lamps
D"> Gamma therapy
34. IR waves are detected by:
A) Thermocouple
B"> Photographic plate
C"> Geiger counter
D"> Scintillation counter
35. Visible light wavelength range:
A) 400 nm to 700 nm
B"> 200 nm to 400 nm
C"> 700 nm to 1 mm
D"> 10 nm to 100 nm
36. UV radiation causes:
A) Skin tanning and cancer
B"> Radioactivity
C"> Nuclear fission
D"> Heating only
37. Ozone layer absorbs:
A) UV radiation
B"> IR radiation
C"> Microwaves
D"> Radio waves
38. X-rays are produced by:
A) Fast electrons hitting metal target
B"> Nuclear decay
C"> Molecular vibrations
D"> Atomic transitions
39. Gamma rays are emitted in:
A) Nuclear reactions
B"> Electronic transitions
C"> Molecular rotations
D"> Crystal vibrations
40. EM waves with highest frequency:
A) Gamma rays
B"> Radio waves
C"> Microwaves
D"> IR waves
41. In solenoid, flux linkage ∝:
A) N²
B"> N
C"> 1/N
D"> N⁰
42. For two coils in series aiding, L_total =:
A) L₁ + L₂ + 2M
B"> L₁ + L₂ - 2M
C"> L₁ + L₂
D"> √(L₁L₂)
43. Coefficient of coupling k =:
A) M/√(L₁L₂)
B"> √(L₁L₂)/M
C"> M/L₁L₂
D"> L₁L₂/M
44. In LR circuit, steady state current I₀ =:
A) V/R
B"> V/L
C"> VL
D"> LR/V
45. Growth of current in inductor: i = I₀(1 - e-t/τ)
A) τ = L/R
B"> τ = R/L
C"> τ = LR
D"> τ = 1/LR
46. Decay of current in inductor: i = I₀e-t/τ
A) τ = L/R
B"> τ = R/L
C"> τ = RL
D"> τ = 1/RL
47. In pure inductor, current leads voltage by:
A) 90°
B"> 0°
C"> 180°
D"> 45°
48. Energy stored in inductor U =:
A) (1/2)LI²
B"> LI²
C"> L/I²
D"> (1/2)L/I²
49. For EM wave E₀/B₀ =:
A) c
B"> 1/c
C"> c²
D"> √c
50. Impedance of free space Z₀ =:
A"> √(μ₀/ε₀) = 377Ω
B"> √(ε₀/μ₀)
C"> μ₀ε₀
D"> 1/√(μ₀ε₀)
51. A circular coil of 50 turns, radius 10 cm in B = 0.5 T perpendicular. If B → 0 in 0.1 s, ε =:
A) 3.93 V
B"> 39.3 V
C"> 0.393 V
D"> 393 V
52. Fleming's right hand rule gives direction of:
A"> Induced emf
B"> Force on conductor
C"> Magnetic field
D"> Current flow
53. In ideal transformer, Vₛ/Vₚ =:
A"> Nₛ/Nₚ
B"> Nₚ/Nₛ
C"> Iₛ/Iₚ
D"> Iₚ/Iₛ
54. Transformer works on:
A"> AC only
B"> DC only
C"> Both AC and DC
D"> Neither
55. In step-up transformer:
A"> Nₛ > Nₚ
B"> Nₚ > Nₛ
C"> Vₛ < Vₚ
D"> Iₛ > Iₚ
56. Hertz experiment confirmed existence of:
A"> EM waves
B"> Photoelectric effect
C"> X-rays
D"> Electrons
57. EM waves are:
A"> Transverse
B"> Longitudinal
C"> Both
D"> Neither
58. Polarisation is possible for:
A"> Transverse waves
B"> Longitudinal waves
C"> Sound waves
D"> All waves
59. In EM waves, phase difference between E and B is:
A"> 0°
B"> 90°
C"> 180°
D"> 270°
60. Momentum of EM wave p =:
A"> U/c
B"> Uc
C"> U
D"> c/U
61. A rod of length 0.2 m moves at 5 m/s ⊥ to B = 0.5 T. ε =:
A"> 0.5 V
B"> 5 V
C"> 0.05 V
D"> 50 V
62. Induced electric field due to changing B is:
A"> Non-conservative
B"> Conservative
C"> Zero
D"> Constant
63. ∮E⋅dl = -dφ_B/dt from:
A"> Faraday's law
B"> Ampere's law
C"> Gauss law
D"> Coulomb's law
64. In capacitor during charging, total current is:
A"> Continuous (conduction + displacement)
B"> Only conduction
C"> Only displacement
D"> Zero
65. Wavelength λ = c/f. For f = 1 GHz, λ =:
A"> 0.3 m
B"> 3 m
C"> 30 m
D"> 300 m
66. Greenhouse effect due to:
A"> IR absorption by CO₂
B"> UV absorption
C"> Visible light
D"> X-rays
67. In perfect reflector, radiation pressure =:
A"> 2I/c
B"> I/c
C"> I/c²
D"> 2Ic
68. Speed of EM waves is least in:
A"> Diamond
B"> Vacuum
C"> Air
D"> Water
69. Refractive index μ =:
A"> c/v
B"> v/c
C"> √(c/v)
D"> c²/v
70. In conductor, EM waves penetrate to depth called:
A"> Skin depth
B"> Critical depth
C"> Penetration depth
D"> Absorption depth
71. 100 turn coil, A = 0.01 m², ΔB = 0.2 T in 0.05 s. ε =:
A"> 4 V
B"> 40 V
C"> 0.4 V
D"> 400 V
72. Lenz's law conserves:
A"> Energy
B"> Momentum
C"> Charge
D"> Mass
73. In AC generator, emf is maximum when coil plane is:
A"> ⊥ to B
B"> || to B
C"> At 45° to B
D"> Any angle
74. RMS value of emf =:
A"> E₀/√2
B"> E₀
C"> E₀√2
D"> 2E₀
75. In DC motor at start, current is high because:
A"> Back emf = 0
B"> Back emf maximum
C"> Resistance zero
D"> Inductance infinite
76. EM waves carry angular momentum due to:
A"> Polarisation
B"> Linear momentum
C"> Energy
D"> Frequency
77. Unpolarised light passed through Polaroid becomes:
A"> Plane polarised
B"> Elliptically polarised
C"> Circularly polarised
D"> Remains unpolarised
78. Two Polaroids at 90° give:
A"> No transmission
B"> 50% transmission
C"> 100% transmission
D"> 25% transmission
79. In vector form, Poynting vector S =:
A"> (1/μ₀)E×B
B"> E×B
C"> μ₀E×B
D"> B×E/μ₀
80. EM wave equation ∇²E = με ∂²E/∂t² from:
A"> Maxwell's equations
B"> Newton's laws
C"> Kirchhoff's laws
D"> Ohm's law
81. A metal ring falls in magnetic field. It experiences:
A"> Retarding force
B"> Accelerating force
C"> No force
D"> Constant velocity
82. Self-inductance L = Nφ/I ∝:
A"> N²
B"> N
C"> 1/N
D"> 1/N²
83. In space propagation, EM wave speed depends on:
A"> ε₀ and μ₀ only
B"> Medium properties
C"> Temperature
D"> Pressure
84. For f = 5 × 10¹⁴ Hz (visible light), λ =:
A"> 600 nm
B"> 600 m
C"> 600 μm
D"> 600 Å
85. X-rays used in:
A"> Medical diagnosis
B"> Cooking
C"> Telecommunication
D"> Heating
86. In transformer core, eddy currents minimised by:
A"> Lamination
B"> Solid core
C"> Air core
D"> Copper core
87. Induced emf depends on:
A"> dφ/dt only
B"> Resistance
C"> Current
D"> Voltage
88. Magnetic flux φ = B⋅A =:
A"> BA cosθ
B"> BA sinθ
C"> BA
D"> B/A
89. When θ = 90° between B and normal, flux =:
A"> Zero
B"> Maximum
C"> BA
D"> BA/2
90. Generator converts:
A"> Mechanical to electrical energy
B"> Electrical to mechanical
C"> Heat to electrical
D"> Chemical to electrical
91. Motor converts:
A"> Electrical to mechanical energy
B"> Mechanical to electrical
C"> Heat to mechanical
D"> Chemical to mechanical
92. In LC oscillations, energy oscillates between:
A"> Electric and magnetic
B"> Kinetic and potential
C"> Heat and work
D"> Chemical and electrical
93. EM waves require no:
A"> Material medium
B"> Source of energy
C"> Electric field
D"> Magnetic field
94. In EM wave, |E|/|B| ratio gives:
A"> Speed of light
B"> Wavelength
C"> Frequency
D"> Intensity
95. Bremsstrahlung produces:
A"> X-rays
B"> Gamma rays
C"> UV rays
D"> IR rays
96. Characteristic X-rays produced by:
A"> Atomic transitions
B"> Nuclear transitions
C"> Molecular vibrations
D"> Free electrons
97. Frequency of AC in India is:
A"> 50 Hz
B"> 60 Hz
C"> 100 Hz
D"> 120 Hz
98. In ideal transformer, power input =:
A"> Power output
B"> Half power output
C"> Double power output
D"> Zero
99. All EM waves travel with speed:
A"> c in vacuum
B"> Different speeds
C"> v < c always
D"> Speed depends on frequency
100. Fundamental source of EM waves:
A"> Accelerated charges
B"> Steady currents
C"> Stationary charges
D"> Uniform motion charges
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