Electromagnetic Field Theory MCQ Questions & Answers

71

Divergence theorem is applicable for . . . . . . . .

A) static field only B) time varying fields only C) both static and time varying fields D) electric fields only

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Answer & Solution

Answer: Option C

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72

Divergence of D is a

A) scalar point function B) vector point function C) phasor D) may be scalar or vector point function

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Answer & Solution

Answer: Option A

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73

An axial magnetic field is applied to a cylindrical rod. The Faraday rotation of a plane polarized beam after emergence from the rod is 5°. If both the field and length of rod or doubled, then the angle of rotations is:

A) 40° B) 5° C) 10° D) 20°

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Answer: Option D

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74

The force between two parallel current carrying conductors placed at a x distance apart and carrying same current I is :

A) $$\frac{{2\pi \times {{10}^{ - 7}}{{\text{I}}^2}}}{{\text{x}}}\frac{{\text{N}}}{{\text{m}}}$$ B) $$\frac{{2 \times {{10}^{ - 7}}{{\text{I}}^2}}}{{\pi {\text{x}}}}\frac{{\text{N}}}{{\text{m}}}$$ C) $$\frac{{2 \times {{10}^{ - 7}}{{\text{I}}^2}}}{{\text{x}}}\frac{{\text{N}}}{{\text{m}}}$$ D) $$\frac{{4\pi \times {{10}^{ - 7}}{{\text{I}}^2}}}{{\text{x}}}\frac{{\text{N}}}{{\text{m}}}$$

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Answer: Option C

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75

The magnetic field inside the solenoid

A) Zero B) Uniform C) Increases with distance from axis D) Decreases with distances from axis

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Answer & Solution

Answer: Option B

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76

If C is a closed curve enclosing a surface S, then the magnetic field intensity $$\overrightarrow H $$, the current density $$\overrightarrow J $$ and the electric flux density $$\overrightarrow D $$ are related by

A) $$\iint\limits_S {\overrightarrow H .\overrightarrow d s = }\oint\limits_C {\left( {J + \frac{{\partial \overrightarrow D }}{{\partial t}}} \right)} .\overrightarrow d l$$ B) $$\int\limits_C {\overrightarrow H .\overrightarrow d \ell = \mathop{{\int\!\!\!\!\!\int}\mkern-21mu \bigcirc}\limits_S {\left( {\overrightarrow J + \frac{{\partial \overrightarrow D }}{{\partial t}}} \right)} } .\overrightarrow d s$$ C) $$\mathop{{\int\!\!\!\!\!\int}\mkern-21mu \bigcirc}\limits_S {\overrightarrow H .\overrightarrow d } s = \int\limits_C {\left( {\overrightarrow J + \frac{{\partial \overrightarrow D }}{{\partial t}}} \right)} .\overrightarrow d l$$ D) $$\oint\limits_C {\overrightarrow H .\overrightarrow d l} = \iint\limits_S {\left( {\overrightarrow J + \frac{{\partial \overrightarrow D }}{{\partial t}}} \right)}.\overrightarrow d s$$

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Answer: Option D

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77

A uniform and constant magnetic field $$B = \hat zB$$ exists in the $$\overrightarrow z $$ direction in vacuum. A particle of mass m with a small charge q is introduced into this region with an initial velocity $$v = \hat x{v_x} + \hat z{v_z}.$$ Given that B, m, q, v_x and v_z are all non-zero. Which one of the following describes the eventual trajectory of the particle?

A) Helical motion in the $${\hat z}$$ direction B) Circular motion in the xy plane C) Linear motion in the $${\hat z}$$ direction D) Linear motion in the $${\hat x}$$ direction

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Answer & Solution

Answer: Option A

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78

Two capacitors C₁ = 20 µF and C₂ = 25 µF with respective breakdown voltages of V₁ = 50 V and V₂ = 40 V are given:

A) Both capacitors can stores the same maximum energy B) When connected up in series and changed C₁ will fail first C) Both capacitors can store the same maximum charge D) When connected up in series and changed C₂ will fail first

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Answer: Option C

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79

A quarter wave transformer can be used for matching accurately

A) Inductive load only B) Capacitive loads only C) Loads with any nature of reactance D) Purely resistive loads only

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Answer & Solution

Answer: Option D

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80

In the relation between the field and the potential, if r < a, then the potential at a point r inside a uniformly charged sphere of radius a, is

A) $$\frac{{{a^3}\rho }}{{3{\varepsilon _0}r}}$$ B) $$\frac{\rho }{{6{\varepsilon _0}}}\left( {3{a^2} - {r^2}} \right)$$ C) $$\frac{{4\pi {a^3}}}{{3r}}$$ D) $$\frac{{2\pi }}{3}\left( {3{a^2} - {r^2}} \right)$$

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Answer: Option B

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Electromagnetic Field Theory MCQ Questions & Answers | ECE