Electromagnetic Field Theory MCQ Questions & Answers

91

If \[\overrightarrow F \left( {\rho ,\,\phi ,\,z} \right) = \rho {{\hat a}_\rho } + \rho {\sin ^2}\phi {{\hat a}_\phi } - z{{\hat a}_z}\] which one of the following is TRUE?

A) \[\nabla .\overrightarrow F \left| {_{\phi = 0}} \right. < \nabla .\overrightarrow F \left| {_{\phi = \frac{\pi }{2}}} \right.\] B) \[\nabla .\overrightarrow F \left| {_{\phi = \frac{\pi }{4}}} \right. = \nabla .\overrightarrow F \left| {_{\phi = 0}} \right.\] C) \[\nabla .\overrightarrow F \left| {_{\phi = 0}} \right. > \nabla .\overrightarrow F \left| {_{\phi = \frac{\pi }{2}}} \right.\] D) \[\nabla .\overrightarrow F \left| {_{\phi = \frac{\pi }{4}}} \right. = 2\nabla .\overrightarrow F \left| {_{\phi = 0}} \right.\]

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Answer & Solution

Answer: Option D

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92

Short circuited stubs are preferred to open-circuited stubs because the latter are

A) More difficult to make and connect B) Made of a transmission line with a different Z₀ C) Liable to radiate D) Incapable of giving a full range of reactance

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Answer & Solution

Answer: Option C

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93

Two metal rings 1 and 2 are placed in a uniform magnetic field which is decreasing with time their planes perpendicular to the field. If the rings are identical except that ring 2 has a thin air gap in it, which one of the following statement is correct?

A) No e.m.f. is induced in ring 1 B) An e.m.f. is induced in both the rings C) Equal Joule heating occurs in both the rings D) Joule heating does not occur in either ring

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Answer & Solution

Answer: Option B

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94

If over the course of a day, the maximum electron density in the ionosphere varies from 10¹¹ to 10¹² m^-3; the critical frequency changes approximately from:

A) 2.2 MHz to 7 MHz B) 2.5 MHz to 8 MHz C) 2.8 MHz to 9 MHz D) 3.2 MHz to 10 MHz

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Answer & Solution

Answer: Option C

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95

An electric charge of Q coulombs is located at the origin. Consider electric potential V and electric field intensity E at any point (x, y, z). Then

A) E and V are both scalars B) E and V are both vector C) E is scalar and V is vector D) E is vector and V is scalar

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Answer & Solution

Answer: Option D

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96

In the infinite plane y = 6m, there exists a uniform surface charge density of $$\frac{1}{{6000\pi }}\mu {\text{C/}}{{\text{m}}^2}$$ the associated electric field strength is

A) $$30\hat i\,{\text{V/m}}$$ B) $$3\hat j\,{\text{V/m}}$$ C) $$30\hat k\,{\text{V/m}}$$ D) $$60\hat j\,{\text{V/m}}$$

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Answer & Solution

Answer: Option B

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97

A plane wave having x-directed electric field propagating in free space along the z-direction is incident on an infinite electrically conducting (perfect conductor) sheet at z = 0 plane. Which one of the following is correct?

A) The sheet will absorb the wave B) There will be x-directed surface electric current on the sheet C) There will be y-directed surface electric current on the sheet D) There will be magnetic current in the sheet

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Answer & Solution

Answer: Option B

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98

The capacitance per unit length and the characteristic impedance of a lossless transmission line are C and Z₀ respectively. The velocity of a travelling wave on the transmission line is

A) $${Z_0}C$$ B) $$\frac{1}{{{Z_0}C}}$$ C) $$\frac{{{Z_0}}}{C}$$ D) $$\frac{C}{{{Z_0}}}$$

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Answer: Option B

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99

An infinite plane Z = 10 m carries a uniformly distributed charge of density 2n C/m². The electric field intensity at the origin is

A) 0.2a_zn V/m B) 2a_zn V/m C) -2a_zn V/m D) -36πa_z V/m

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Answer & Solution

Answer: Option D

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100

An elliptically polarized wave travelling in the positive Z-direction in air has x and y components
E_x = 3sin(ωt - βz) V/m E_y = 6sin(ωt - βz + 75°) V/m

A) 8 W/m² B) 4 W/m² C) 62.5 mW/m² D) 125 mW/m²

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Answer & Solution

Answer: Option C

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Electromagnetic Field Theory MCQ Questions & Answers | ECE