Electromagnetic Field Theory MCQ Questions & Answers

81

A force with which the plates of a parallel plate capacitor having charge Q and area of each plate A, attract each other is:
1. directly proportional to Q
2. directly proportional to Q²
3. inversely proportional to A
Of these statements which are correct?

A) 1 and 2 only B) 2 and 3 only C) 1 and 3 only D) 1, 2 and 3

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Answer & Solution

Answer: Option B

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82

A quarter-wave transformer matching a 75 Ω source with a 300 Ω load should have a characteristic impedance of

A) 50 Ω B) 100 Ω C) 150 Ω D) 200 Ω

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Answer & Solution

Answer: Option C

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83

The phase velocity of a plane wave given by E_x = E₀ cos(ωt - βz) with a frequency of 5.0 GHz and a wavelength in the material medium of 3.0 cm is:

A) 3.0 × 10⁸ m/sec B) 1.5 × 10⁸ m/sec C) 5 × 10⁸ m/sec D) None

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Answer & Solution

Answer: Option B

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84

A plane wave of wavelength λ is travelling in a direction making an angle 30° with positive x-axis and 90° with positive y-axis. The $$\overrightarrow E $$ field of the plane wave can be represented as (E₀ is a constant)

A) $$\overrightarrow E = \hat y{E_0}{e^{j\left( {\omega t - \frac{{\sqrt 3 \pi }}{\lambda }x - \frac{\pi }{\lambda }z} \right)}}$$ B) $$\overrightarrow E = \hat y{E_0}{e^{j\left( {\omega t - \frac{\pi }{\lambda }x - \frac{{\sqrt 3 \pi }}{\lambda }z} \right)}}$$ C) $$\overrightarrow E = \hat y{E_0}{e^{j\left( {\omega t + \frac{{\sqrt 3 \pi }}{\lambda }x + \frac{\pi }{\lambda }z} \right)}}$$ D) $$\overrightarrow E = \hat y{E_0}{e^{j\left( {\omega t - \frac{\pi }{\lambda }x + \frac{{\sqrt 3 \pi }}{\lambda }z} \right)}}$$

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Answer & Solution

Answer: Option A

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85

A boundary separates two magnetic materials of permeability µ₁ and µ₂. The magnetic field vector in µ₁ is H₁ with a normal component H_n₁ and tangential component H_t₁ while that in µ₂ is H₂ with normal component H_n₂ and a tangential component H_t₂. Then the derived conditions would be

A) H₁ = H₂ and H_t₁ = H_t₂ B) H_t₁ = H_t₂ and µ₁H_n₁ = µ₂H_n₂ C) H₁ = H₂ and µ₁H_n₁ = µ₂H_n₂ D) H₁ = H₂, H_t₁ = H_t₂ and µ₁H_n₁ = µ₂H_n₂

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Answer & Solution

Answer: Option B

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86

Consider an impedance Z = R + jX marked with point P in an impedance Smith chart as shown in figure. The movement from point P along a constant resistance circle in the clockwise direction by an angle 45° is equivalent to-
Electromagnetic Field Theory mcq question image

Electromagnetic Field Theory mcq question image

A) adding an inductance in series with Z B) adding a capacitance in series with Z C) adding an inductance in shunt across Z D) adding a capacitance in shunt across Z

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Answer & Solution

Answer: Option A

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87

An electromagnetic wave having frequency f₀ gets attenuated by a factor of e^-2 after propagating a distance d in a good conductor. If the signal frequency is now reduced to 0.5 f₀, after travelling the same distance d in the same conductor, the signal will get attenuated by a factor of:

A) e^-4 B) e^-2√2 C) e^-√2 D) e^-1

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Answer & Solution

Answer: Option C

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88

The wave which 'lie down and dies' is called

A) Space wave B) Ground wave C) Sky wave D) Spherical wave

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Answer & Solution

Answer: Option B

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89

If a lossless line is terminated with a load impedance 40 + j30 Ω, then the characteristic impedance of the line for minimum possible standing wave ratio (SWR) will be

A) 70 Ω B) 25 Ω C) 50 Ω D) 100 Ω

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Answer & Solution

Answer: Option C

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90

Two thin parallel wires are carrying current along the same direction. The force experienced by one due to the other is:

A) Parallel to the lines B) Perpendicular to the lines and attractive C) Perpendicular to the lines and repulsive D) Zero

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Answer & Solution

Answer: Option B

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Electromagnetic Field Theory MCQ Questions & Answers | ECE