1. The phenomenon of electromagnetic induction was discovered by:
A) Michael Faraday
B) Heinrich Lenz
C) James Clerk Maxwell
D) Hans Christian Oersted
2. Faraday’s first law of electromagnetic induction states that:
A) An emf is induced when magnetic flux changes
B) The induced emf is proportional to the rate of change of flux
C) The direction of induced emf opposes the change
D) Induced current depends on resistance
3. The SI unit of magnetic flux is:
A) Tesla
B) Weber
C) Henry
D) Gauss
4. 1 Weber is equal to:
A) 10⁸ Maxwell
B) 10⁴ Maxwell
C) 10⁶ Maxwell
D) 10¹⁰ Maxwell
5. The induced emf in a coil is given by:
A) \(\varepsilon = -\frac{d\phi}{dt}\)
B) \(\varepsilon = -N\frac{d\phi}{dt}\)
C) \(\varepsilon = \frac{d\phi}{dt}\)
D) \(\varepsilon = N\frac{dB}{dt}\)
6. Lenz’s law is based on the principle of conservation of:
A) Charge
B) Energy
C) Momentum
D) Mass
7. When a bar magnet is pushed towards a coil, the induced current in the coil:
A) Produces a magnetic field opposing the motion
B) Aids the motion of the magnet
C) Has no effect
D) Depends on resistance
8. The magnetic flux through a loop is \(\phi = B A \cos\theta\). If \(\theta = 90^\circ\), flux is:
A) Zero
B) Maximum
C) \(BA\)
D) \(BA/2\)
9. A coil of 100 turns and area 0.01 m² is in a magnetic field of 0.2 T perpendicular to it. If the field is reduced to zero in 0.1 s, the induced emf is:
A) 2 V
B) 20 V
C) 0.2 V
D) 200 V
10. Self-inductance of a coil is analogous to:
A) Inertia in mechanics
B) Capacitance
C) Resistance
D) Conductance
11. The unit of inductance is:
A) Weber
B) Henry
C) Tesla
D) Faraday
12. Energy stored in an inductor is:
A) \(\frac{1}{2}CV^2\)
B) \(\frac{1}{2}LI^2\)
C) \(LI\)
D) \(\frac{L}{I}\)
13. In an AC generator, the emf is maximum when the plane of the coil is:
A) Parallel to the magnetic field
B) Perpendicular to the magnetic field
C) At 45° to the field
D) Zero when parallel
14. The frequency of emf in an AC generator depends on:
A) Speed of rotation
B) Number of turns
C) Area of coil
D) Magnetic field strength
15. Electromagnetic waves were predicted by:
A) Maxwell
B) Hertz
C) Faraday
D) Marconi
16. In electromagnetic waves, the electric and magnetic fields are:
A) Parallel to each other
B) Perpendicular to each other and to the direction of propagation
C) In the same direction as propagation
D) Randomly oriented
17. The speed of electromagnetic waves in vacuum is:
A) \(3 \times 10^8\) m/s
B) \(3 \times 10^6\) m/s
C) \(3 \times 10^{10}\) m/s
D) \(1.5 \times 10^8\) m/s
18. The relation \(c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}\) was derived by:
A) Faraday
B) Maxwell
C) Hertz
D) Ampere
19. Electromagnetic waves are:
A) Longitudinal
B) Transverse
C) Both
D) Neither
20. The Poynting vector represents:
A) Energy flux density of EM wave
B) Momentum of photon
C) Electric field intensity
D) Magnetic flux
21. In EM waves, \(E_0 / B_0 =\):
A) \(c\)
B) \(1/c\)
C) \(c^2\)
D) \(1/c^2\)
22. The average energy density of electric field in EM wave is:
A) \(\frac{1}{2} \epsilon_0 E^2\)
B) \(\epsilon_0 E^2\)
C) \(\frac{1}{4} \epsilon_0 E^2\)
D) \(2 \epsilon_0 E^2\)
23. The electromagnetic spectrum in increasing order of frequency is:
A) Radio, Microwave, IR, Visible, UV, X-ray, Gamma
B) Gamma, X-ray, UV, Visible, IR, Microwave, Radio
C) Visible, IR, UV, X-ray, Gamma, Radio, Microwave
D) Microwave, Radio, IR, Visible, UV, X-ray, Gamma
24. Which of the following is not an electromagnetic wave?
A) Sound wave
B) Radio wave
C) X-ray
D) Gamma ray
25. The wavelength range of visible light is:
A) 400 nm to 700 nm
B) 200 nm to 400 nm
C) 700 nm to 1000 nm
D) 100 nm to 200 nm
26. Eddy currents are produced in a metallic conductor when:
A) It is placed in a changing magnetic field
B) A steady current flows through it
C) It is insulated
D) It is at rest
27. Eddy currents are minimized in transformers by using:
A) Solid iron core
B) Laminated iron core
C) Copper core
D) No core
28. An induced emf has no effect if the circuit is:
A) Open
B) Closed with high resistance
C) Closed with low resistance
D) Made of insulator
29. Mutual inductance between two coils depends on:
A) Number of turns
B) Area of coils
C) Distance between them
D) All of the above
30. The dimensional formula of magnetic flux is:
A) MLT⁻²A⁻¹
B) ML²T⁻²A⁻¹
C) ML²T⁻¹A⁻¹
D) MLT⁻¹A⁻¹
31. A circular loop of radius 0.1 m carries a current of 2 A. The magnetic flux through the loop is (μ₀ = 4π × 10⁻⁷):
A) 4π × 10⁻⁸ Wb
B) 2π × 10⁻⁷ Wb
C) 4π × 10⁻⁷ Wb
D) Zero
32. A coil rotates in a magnetic field. The induced emf is zero when the angle between normal to plane and B is:
A) 0°
B) 90°
C) 45°
D) 180°
33. The back emf in a motor:
A) Opposes the applied voltage
B) Aids the applied voltage
C) Is zero at start
D) Both A and C
34. In a DC motor, the starting current is high because:
A) Back emf is zero
B) Resistance is high
C) Inductance is zero
D) Voltage is low
35. The displacement current was introduced by:
A) Maxwell
B) Faraday
C) Ampere
D) Lenz
36. Displacement current is due to:
A) Flow of electrons
B) Changing electric field
C) Magnetic field
D) Resistance
37. The conduction current in a wire and displacement current in a capacitor are:
A) Equal in magnitude in series
B) Different
C) Zero in capacitor
D) Infinite
38. The wavelength of a radio wave of frequency 100 MHz is:
A) 3 m
B) 30 m
C) 300 m
D) 0.3 m
39. Infrared waves are produced by:
A) Hot bodies
B) Radioactive decay
C) Atomic transitions
D) All of the above
40. Which EM wave has the highest penetrating power?
A) UV rays
B) X-rays
C) Gamma rays
D) Microwaves
41. The ozone layer absorbs:
A) Infrared radiation
B) Ultraviolet radiation
C) Microwaves
D) Radio waves
42. In a solenoid, the self-inductance is proportional to:
A) \(N^2\)
B) \(N\)
C) \(1/N\)
D) \(1/N^2\)
43. Two coils of self-inductance L₁ and L₂ are in series. Total inductance if mutually aiding:
A) L₁ + L₂ + 2M
B) L₁ + L₂ - 2M
C) L₁ + L₂
D) (L₁L₂)^0.5
44. A metal sheet is moved in a magnetic field. Eddy currents cause:
A) Heating
B) Cooling
C) No effect
D) Magnetization
45. The induced electric field in a region of changing magnetic field is:
A) Conservative
B) Non-conservative
C) Zero
D) Uniform
46. The direction of induced emf is given by:
A) Fleming’s right-hand rule
B) Fleming’s left-hand rule
C) Right-hand thumb rule
D) Left-hand thumb rule
47. A coil is rotated in a uniform magnetic field. The induced emf is:
A) Sinusoidal
B) Constant
C) Zero
D) Triangular
48. The peak value of emf in an AC generator is \(E_0 = NAB\omega\). The rms value is:
A) \(E_0 / \sqrt{2}\)
B) \(E_0\)
C) \(E_0 / 2\)
D) \(2E_0\)
49. Electromagnetic waves transport:
A) Energy
B) Momentum
C) Both energy and momentum
D) Neither
50. The intensity of EM wave is proportional to:
A) \(E_0^2\)
B) \(E_0\)
C) \(1/E_0^2\)
D) \(1/E_0\)
51. The pressure exerted by EM waves is called:
A) Radiation pressure
B) Atmospheric pressure
C) Magnetic pressure
D) Electric pressure
52. Which of the following can produce EM waves?
A) Accelerated charge
B) Steady current
C) Stationary charge
D) Uniform motion charge
53. The EM wave with lowest frequency is:
A) Radio wave
B) Microwave
C) Infrared
D) Visible light
54. A plane EM wave travels in vacuum along z-direction. E vector is along x-axis. Then B is along:
A) y-axis
B) z-axis
C) x-axis
D) Any direction
55. The velocity of EM waves in a medium is \(v = 1/\sqrt{\mu \epsilon}\). This is called:
A) Phase velocity
B) Group velocity
C) Drift velocity
D) Signal velocity
56. In a perfect conductor, EM waves:
A) Are reflected
B) Are absorbed
C) Pass through
D) Are refracted
57. The skin depth is inversely proportional to:
A) Frequency
B) Conductivity
C) Permeability
D) All of the above
58. A changing magnetic field produces:
A) Electric field
B) Magnetic field
C) Both
D) None
59. The induced emf in a rod moving in a magnetic field is:
A) \(B l v\)
B) \(B l v \sin\theta\)
C) \(B l / v\)
D) Zero if parallel
60. The force on a charged particle moving in EM wave is called:
A) Lorentz force
B) Coulomb force
C) Gravitational force
D) Nuclear force
61. A rectangular loop is pulled out of a magnetic field with constant velocity. The induced emf is:
A) \(B l v\)
B) \(B l^2 v\)
C) \(B a v\)
D) Zero
62. The emf induced in a rotating rod in a uniform B field is:
A) \(\frac{1}{2} B \omega l^2\)
B) \(B \omega l\)
C) \(B \omega l^2\)
D) Zero
63. The mutual inductance M is maximum when coils are:
A) Coaxial
B) Perpendicular
C) Parallel but far
D) Antiparallel
64. The time constant of an LR circuit is:
A) L/R
B) R/L
C) LR
D) 1/LR
65. In an inductor, current lags voltage by:
A) 90°
B) 0°
C) 180°
D) 45°
66. The energy density in magnetic field is:
A) \(\frac{B^2}{2\mu_0}\)
B) \(\frac{B^2}{\mu_0}\)
C) \(\frac{\mu_0 B^2}{2}\)
D) \(\mu_0 B^2\)
67. The average power in EM wave is:
A) \(\frac{1}{2} \epsilon_0 E_0^2 c\)
B) \(\epsilon_0 E_0^2 c\)
C) \(\frac{1}{4} \epsilon_0 E_0^2 c\)
D) \(2 \epsilon_0 E_0^2 c\)
68. Microwaves are used in:
A) Radar
B) Cooking
C) Communication
D) All of the above
69. The greenhouse effect is due to:
A) Infrared radiation
B) Ultraviolet radiation
C) Visible light
D) Radio waves
70. X-rays are produced when:
A) Fast electrons are stopped by a target
B) Atoms are ionized
C) Molecules vibrate
D) Nuclei decay
71. The frequency of UV light is higher than:
A) Visible light
B) Infrared
C) Microwaves
D) All of the above
72. A coil has 200 turns, area 0.05 m², B = 0.1 T. If B becomes zero in 0.01 s, induced emf is:
A) 10 V
B) 100 V
C) 1 V
D) 0.1 V
73. If the number of turns in a coil is doubled, induced emf becomes:
A) Doubled
B) Halved
C) Quadrupled
D) Unchanged
74. The magnetic field inside a long solenoid is:
A) Zero
B) \(\mu_0 n I\)
C) \(\mu_0 n / I\)
D) Infinite
75. The inductance of a solenoid is proportional to:
A) \(n^2\)
B) \(n\)
C) \(1/n\)
D) \(1/n^2\)
76. In EM induction, the induced emf is independent of:
A) Resistance of circuit
B) Number of turns
C) Rate of change of flux
D) Area of coil
77. The direction of induced current is such that it:
A) Opposes the change in flux
B) Aids the change
C) Is random
D) Is zero
78. A copper ring is dropped in a magnetic field. It will:
A) Fall with acceleration less than g
B) Fall with g
C) Remain suspended
D) Move up
79. The induced emf in a stationary coil in a changing magnetic field is due to:
A) Change in flux
B) Motion of coil
C) Resistance
D) Current in coil
80. The EM wave equation is derived from:
A) Maxwell’s equations
B) Faraday’s law only
C) Ampere’s law only
D) Gauss’s law only
81. The impedance of free space is:
A) 377 Ω
B) 300 Ω
C) 120 π Ω
D) Both A and C
82. The Hertz experiment demonstrated:
A) Production and detection of EM waves
B) Photoelectric effect
C) Interference of light
D) Diffraction
83. The wavelength of gamma rays is of the order of:
A) 10⁻¹² m
B) 10⁻⁶ m
C) 10⁻³ m
D) 10 m
84. The frequency of visible light is approximately:
A) 10¹⁴ Hz
B) 10⁸ Hz
C) 10⁶ Hz
D) 10¹⁸ Hz
85. The EM waves used in remote sensing are:
A) Microwaves
B) Infrared
C) Both
D) UV
86. The phenomenon of electromagnetic induction is used in:
A) Transformer
B) Generator
C) Motor
D) All of the above
87. The induced emf lasts as long as:
A) Flux is changing
B) Coil is moving
C) Current is flowing
D) Magnet is present
88. The magnetic flux is maximum when the angle between B and normal to the plane is:
A) 0°
B) 90°
C) 180°
D) 45°
89. In a uniform magnetic field, a loop is rotated. The induced emf varies as:
A) sin ωt
B) cos ωt
C) Both possible
D) Constant
90. The self-induced emf opposes the:
A) Change in current
B) Steady current
C) Voltage
D) Resistance
91. The growth of current in an inductor is:
A) Exponential
B) Linear
C) Parabolic
D) Sudden
92. The decay of current in an inductor is:
A) Exponential
B) Linear
C) Instantaneous
D) Oscillatory
93. The EM waves do not require:
A) Medium
B) Charge acceleration
C) Electric field
D) Magnetic field
94. The polarization of EM waves indicates:
A) Direction of E field
B) Direction of B field
C) Direction of propagation
D) Wavelength
95. Unpolarized light can be polarized by:
A) Reflection
B) Scattering
C) Polaroid
D) All of the above
96. The speed of EM waves is maximum in:
A) Vacuum
B) Air
C) Water
D) Glass
97. The refractive index of a medium for EM waves is:
A) \(c/v\)
B) \(v/c\)
C) \(c^2/v^2\)
D) \(v^2/c^2\)
98. The EM waves follow the principle of:
A) Superposition
B) Conservation of energy
C) Huygens principle
D) All of the above
99. The momentum carried by an EM wave is:
A) \(E/c\)
B) \(E c\)
C) \(p = E/c\) for photon
D) Both A and C
100. The source of all EM waves is:
A) Accelerated charges
B) Steady charges
C) Magnets
D) Gravity
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