## Objective Questions on Maxwell’s Equations and Electromagnetic Waves

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Antenna Fundamental Parameters MCQ

### Multiple Choice Questions

Q.1. Maxwell’s equations shelter on __________ law(s).

- Faraday’s
- Gauss’s
- Ampere’s
- All of these

**Answer: **All of these

Q.2. Conduction current through a wire is __________ displacement current in capacitor.

- Same as
- Different from

- Twice of

- None of these

**Answer: **Same as

Q.3. Absolute permeability of free space is

- 4π × 10
^{-7}A/m - 4π × 10
^{-7}H/m - 4π × 10
^{-7}F/m - 4π × 10
^{-7}H/m^{2}

**Answer: **4π × 10^{-7} H/m

Q.4. For static magnetic field,

- ∇ ×
**B**= ρ - ∇ ×
**B**= μ**J** - ∇ ×
**B**= μ_{0}**J** - ∇ ×
**B**= 0

**Answer: **∇ × **B** = μ**J**

Q.5. The time varying electric field is

**E**= − ∇V**E**= − ∇V −**Ȧ****E**= − ∇V –**B****E**= − ∇V –**D**

**Answer: ****E** = − ∇V − **Ȧ**

Q.6. Maxwell’s third equation gives __________.

- \bigtriangledown \times \vec{H}=\vec{J_{d}}+\frac{\partial \rho }{\partial t}
- \bigtriangledown \cdot \vec{H}=J_{d}\frac{\partial \rho }{\partial t}
- \bigtriangledown \cdot \vec{H}=\vec{J_{d}}+\frac{\partial \rho }{\partial t}
- \bigtriangledown \times \vec{H}=J_{d}\frac{\partial \rho }{\partial t}

**Answer: **\bigtriangledown \times \vec{H}=\vec{J_{d}}+\frac{\partial \rho }{\partial t}

Q.7. Maxwell’s fourth equation gives __________.

- \bigtriangledown \cdot \vec{E}=-\frac{\partial \vec{B} }{\partial t}
- \bigtriangledown \times \vec{E}=-\frac{\partial \vec{B} }{\partial t}
- \bigtriangledown \cdot \vec{E}=\frac{\partial \vec{B} }{\partial t}
- \bigtriangledown \times \vec{E}=\frac{\partial \vec{B} }{\partial t}

**Answer: **\bigtriangledown \times \vec{E}=-\frac{\partial \vec{B} }{\partial t}

Q.8. In empty space, conduction current is __________.

- Infinity

- Unity
- Zero
- None of these

**Answer: **Zero

Q.9. As per Maxwell’s first equation __________.

- \bigtriangledown \times \vec{D}=\rho _{\nu }
- \bigtriangledown \cdot \vec{D}=\rho _{\nu }
- \bigtriangledown \times \vec{D}=\rho _{s }
- \bigtriangledown \cdot \vec{D}=\rho _{s }

**Answer: **\bigtriangledown \cdot \vec{D}=\rho _{\nu }

Q.10. Maxwell’s second equation gives __________.

- \bigtriangledown \times \vec{B}=0
- \bigtriangledown \cdot \vec{B}=0
- \bigtriangledown \times \vec{B}=1
- \bigtriangledown \cdot \vec{B}=1

**Answer: **\bigtriangledown \cdot \vec{B}=0

Q.11. emf is closed __________ integral of non-conservational electric field that is generated by battery.

- Line
- Surface
- Volume
- None of these

**Answer: **Line

Q.12. Maxwell’s equations in __________ form give unformation at points of discontinuity in electromagnetic fields.

- Differential
- Integral
- Algebraic
- None of these

**Answer: **Integral

Q.13. At the point of discontinuity, __________ component of magnetic flux density is continuous.

- Tangential
- Normal
- None of these
- Cannot say

**Answer: **Normal

Q.14. For those surfaces where surface charge density is __________ normal component of electric flux density is continuous.

- Infinity
- Unity
- Zero
- None of these

**Answer: **Zero

Q.15. Displacement current density ____________ current passing through a capacitor.

- Represents
- Does not represent
- Is the same as
- None of these

**Answer: **Does not represent

Q.16. Line integral of an electric field around a closed path is __________.

- Infinity
- Unity
- Zero
- None of these

**Answer: **Zero

Q.17. __________ are caused by accelerated charges.

- Time-varying fields
- Waves
- Both Time-varying fields & Waves
- None of these

**Answer: **Both Time-varying fields & Waves

Q.18. Maxwell’s equations give the relations between

- different fields
- different sources
- different boundary conditions
- none of these

**Answer: **different fields

Q.19. cosine of the angle between the two vectors is

- sum of the products of the directions of the two vectors
- difference of the products of the directions of the two vectors
- product of the products of the directions of the two vectors
- none of these

**Answer: **sum of the products of the directions of the two vectors

Q.20. The electric field intensity, E at a point (1, 2, 2) due to (1/9) nc located at (0, 0, 0) is

- 33 V/m
- 0.333 V/m
- 0.33 V/m
- Zero

**Answer: **0.33 V/m

Q.21. If **E** is a vector, then ∇ . ∇ × **E** is

- 0
- 1
- does not exist
- none of these

**Answer: **0

Q.22. For free space,

- σ = ∞
- σ =0
- J ≠ 0
- none of these

**Answer: **σ =0

Q.23. The electric field for time varying potentials

- E = − ∇V
- E = − ∇V –
**A** - E = ∇V
- E = − ∇V +
**A**

**Answer: **E = − ∇V

Q.24. The intrinsic impedence of the medium whose σ = 0, ∈_{r} = 9, μ_{r} = 1 is

- 40 πΩ
- 9 Ω
- 120 πΩ
- 60 πΩ

**Answer: **40 πΩ

Q.25 For time varying EM fields

- ∇ ×
**H**=**J** - ∇ ×
**H**=**Ḋ**+**J** - ∇ ×
**E**= 0 - none of these

**Answer: **∇ × **H** = **Ḋ** + **J**

Q.26. The wavelength of a wave with a propagation constant = 0.1π + j 0.2π is

- 10 m
- 20 m
- 30 m
- 25 m

**Answer: **10 m

Q.27. The electric field just above a conductor is always

- normal to the surface
- tangential to source
- zero
- ∞

**Answer: **normal to the surface

Q.28. The normal components of D are

- continuous across a dielectric boundary
- discontinuous across a dielectric boundary
- zero
- ∞

**Answer: **continuous across a dielectric boundary

Q.29. If J_{c} = 1 mA/m^{2} in a medium whose conductivity is σ = 10 Mho/m, E is

- 0.1 V/m
- 10μ V/m
- 1.0μ V/m
- 10 V/m.

**Answer: **0.1 V/m

Q.30. If J_{d} = 2 mA/m^{2} in a medium whose ∈_{r} = 2, σ= 4.95 Mho/m at a frequency of 1 GHz, J_{c} is

- 8.9 mA/m
^{2} - 89 mA/m
^{2} - 0.89 mA/m
^{2} - 89 A/m
^{2}

**Answer: **89 mA/m^{2}