Electromagnetic Fields and Waves MCQs

1. Which of the following equations represents Faraday’s law of electromagnetic induction?
A) ∇⋅E = ρ / ϵ₀
B) ∇⋅B = 0
C) ∇×E = −∂B / ∂t
D) ∇×B = μ₀J

Answer: C

2. The speed of light in a vacuum is approximately:
A) 3 × 10⁶ m/s
B) 3 × 10⁸ m/s
C) 3 × 10¹⁰ m/s
D) 3 × 10² m/s

Answer: B

3. Which one of Maxwell’s equations describes the relationship between electric charges and electric fields?
A) Gauss’s law for electricity
B) Gauss’s law for magnetism
C) Faraday’s law of electromagnetic induction
D) Ampère’s law

Answer: A

4. In electromagnetic waves, the electric field and magnetic field are:
A) parallel to each other
B) perpendicular to each other
C) anti-parallel to each other
D) in the same direction

Answer: B

5. Which of the following electromagnetic waves has the highest frequency?
A) Radio waves
B) Microwaves
C) X-rays
D) Infrared radiation

Answer: C

6. The SI unit of magnetic flux is:
A) Ohm
B) Weber
C) Tesla
D) Henry

Answer: B

7. An alternating current (AC) circuit consists of a resistor, an inductor, and a capacitor in series. The phase relationship between the voltage and current in the circuit is:
A) Voltage leads current
B) Current leads voltage
C) Voltage and current are in phase
D) Voltage and current are out of phase by 90 degrees

Answer: D

8. The wavelength of an electromagnetic wave is:
A) the distance between two consecutive crests or troughs
B) the distance between the source and the receiver
C) the time period of the wave
D) the speed of the wave divided by its frequency

Answer: A

9. Which one of the following materials exhibits the highest permeability?
A) Air
B) Water
C) Iron
D) Glass

Answer: C

10. In an LC circuit, resonance occurs when:
A) the inductive reactance equals the capacitive reactance
B) the resistance is zero
C) the inductance is zero
D) the capacitance is zero

Answer: A

11. The radiation pattern of a half-wave dipole antenna in free space is:
A) omnidirectional
B) unidirectional
C) bidirectional
D) isotropic

Answer: B

12. The phenomenon of total internal reflection occurs when light travels from:
A) a rarer medium to a denser medium
B) a denser medium to a rarer medium
C) one medium to another with the same refractive index
D) a medium with a higher refractive index to a lower refractive index

Answer: B

13. The principle of superposition applies to:
A) mechanical waves only
B) electromagnetic waves only
C) both mechanical and electromagnetic waves
D) standing waves only

Answer: C

14. The skin effect in conductors increases with:
A) increasing frequency
B) decreasing frequency
C) increasing temperature
D) decreasing temperature

Answer: A

15. An electromagnetic wave is incident on a medium with higher refractive index than the surrounding medium. This will result in:
A) reflection and refraction
B) only reflection
C) only refraction
D) absorption

Answer: A

16. Which of the following statements about the Poynting vector S is correct?
A) It represents the electric field intensity
B) It represents the magnetic field intensity
C) It represents the direction of propagation of electromagnetic waves
D) It is zero everywhere in space

Answer: C

17. The energy stored in a capacitor is given by:
A) 1/2 CV²
B) 1/2 Q² / C
C) 1/2 QV
D) 1/2 Q² / V

Answer: A

18. Which of the following materials is typically used as a dielectric in capacitors?
A) Copper
B) Silver
C) Mica
D) Aluminum

Answer: C

19. Electromagnetic waves are generated by:
A) stationary charges
B) time-varying electric fields
C) steady currents
D) magnetic monopoles

Answer: B

20. The phenomenon of polarization of light is related to:
A) the electric field vector
B) the magnetic field vector
C) the intensity of light
D) the wavelength of light

Answer: A

21. Which of the following is a characteristic of a good antenna?
A) Low resistance
B) High capacitance
C) Low inductance
D) High gain

Answer: D

22. The unit of inductance is the:
A) Henry
B) Volt
C) Ampere
D) Weber

Answer: A

23. The capacitance of a parallel plate capacitor is directly proportional to:
A) the area of the plates
B) the distance between the plates
C) the voltage across the plates
D) the dielectric constant of the material between the plates

Answer: A

24. Which of the following is true about electromagnetic waves in a vacuum?
A) They require a medium for propagation
B) They have a constant speed
C) They have a wavelength of zero
D) They are longitudinal waves

Answer: B

25. A wave has a frequency of 5 Hz. What is its period?
A) 0.05 s
B) 0.2 s
C) 2 s
D) 5 s

Answer: C

26. In a transformer, the primary coil has 100 turns and the secondary coil has 200 turns. If the primary coil is connected to a 120V AC supply, the secondary voltage will be:
A) 120V
B) 240V
C) 60V
D) 30V

Answer: B

27. The magnetic field inside a long solenoid carrying current is:
A) uniform
B) non-uniform
C) zero
D) infinitely large

Answer: A

28. Which of the following electromagnetic waves has the longest wavelength?
A) Gamma rays
B) X-rays
C) Radio waves
D) Ultraviolet rays

Answer: C

29. The process of reducing unwanted reflections in optical devices is known as:
A) diffraction
B) interference
C) polarization
D) anti-reflection coating

Answer: D

30. The electric flux through a closed surface is related to the net electric charge enclosed by:
A) Gauss’s law
B) Ampère’s law
C) Faraday’s law
D) Lenz’s law

Answer: A

31. Which of the following electromagnetic waves is used for communication with satellites?
A) Gamma rays
B) X-rays
C) Microwaves
D) Ultraviolet rays

Answer: C

32. The concept of “self-inductance” in an electric circuit is analogous to:
A) resistance
B) capacitance
C) magnetic permeability
D) mutual inductance

Answer: B

33. The critical angle for total internal reflection depends on:
A) the angle of incidence and the angle of reflection
B) the refractive indices of the two media
C) the frequency of the incident light
D) the polarization of the incident light

Answer: B

34. A wave has a wavelength of 0.1 meters and a frequency of 3 MHz. What is its speed?
A) 3 × 10⁵ m/s
B) 3 × 10⁶ m/s
C) 3 × 10⁷ m/s
D) 3 × 10⁸ m/s

Answer: B

35. Which of the following statements about Maxwell’s equations is correct?
A) There are 3 equations
B) There are 4 equations
C) There are 5 equations
D) There are 6 equations

Answer: B

36. The phenomenon of electromagnetic induction is used in the operation of:
A) capacitors
B) transformers
C) resistors
D) inductors

Answer: B

37. Which of the following statements is true for a convex lens?
A) It converges parallel light rays to a point
B) It diverges parallel light rays
C) It has a negative focal length
D) It cannot form real images

Answer: A

38. The unit of electric field strength is:
A) Tesla
B) Coulomb
C) Newton
D) Volt per meter

Answer: D

39. The frequency of an electromagnetic wave is doubled. What happens to its wavelength, assuming the speed of light remains constant?
A) It is doubled
B) It is halved
C) It remains the same
D) It is quadrupled

Answer: B

40. A step-up transformer:
A) increases voltage and decreases current
B) decreases voltage and increases current
C) increases both voltage and current
D) decreases both voltage and current

Answer: A

41. The energy carried by an electromagnetic wave is proportional to its:
A) frequency
B) wavelength
C) speed
D) amplitude

Answer: A

42. The antenna used for FM radio broadcasting is typically a:
A) dipole antenna
B) Yagi-Uda antenna
C) parabolic reflector antenna
D) loop antenna

Answer: A

43. The index of refraction of a medium is:
A) the speed of light in vacuum divided by the speed of light in the medium
B) the speed of light in the medium divided by the speed of light in vacuum
C) the reciprocal of the speed of light in the medium
D) the reciprocal of the speed of light in vacuum

Answer: A

44. Which of the following is a property of electromagnetic waves but not of sound waves?
A) They can travel through vacuum
B) They require a medium for propagation
C) They are transverse waves
D) They have reflection and refraction properties

Answer: A

45. A material is said to be diamagnetic if:
A) it has a positive magnetic susceptibility
B) it has a negative magnetic susceptibility
C) it has no magnetic susceptibility
D) it has a very high magnetic susceptibility

Answer: B

46. The power radiated by an antenna is proportional to the square of its:
A) wavelength
B) frequency
C) length
D) current

Answer: D

47. Which of the following devices converts electrical signals into light signals?
A) Resistor
B) Capacitor
C) Diode
D) LED

Answer: D

48. A wave has a frequency of 50 Hz. What is its period?
A) 0.02 s
B) 0.04 s
C) 0.2 s
D) 20 s

Answer: C

49. The phenomenon of diffraction occurs when waves:
A) change direction upon passing through a slit
B) reflect off a surface at an angle
C) undergo total internal reflection
D) pass through a medium with varying refractive index

Answer: A

50. The impedance of free space is approximately equal to:
A) 377 ohms
B) 1 ohm
C) 1,000 ohms
D) 1,000,000 ohms

Answer: A

Electromagnetic Fields and Waves MCQs

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