Electromagnetic Theory Questions and Answers – Intrinsic Impedance and Propagation Constant

This set of Electromagnetic Theory Questions and Answers for Aptitude test focuses on “Intrinsic Impedance and Propagation Constant”.

1. The intrinsic impedance of a wave with electric and magnetic field of 10 and 8 respectively is
a) 1.6
b) 1.11
c) 1.25
d) 0.8

Explanation: The intrinsic impedance of a wave is given by η = √(E/H). on substituting for E = 10 and H = 8, we get η = 1.11 units.

2. The intrinsic impedance is defined as the ratio of the magnetic field to the electric field of the electromagnetic wave. State true/false
a) True
b) False

Explanation: The intrinsic impedance is defined as the ratio of the electric field intensity to the magnetic field intensity. It is denoted by η. It is a complex quantity.

3. The intrinsic impedance in free space is
a) 60π
b) 12π
c) 6π
d) 120π

Explanation: The intrinsic impedance of the free space is the ratio of the permittivity to the permeability. For air medium, the value is 120π or 377 ohm.

4. The propagation constant is a complex quantity. State true/false.
a) True
b) False

Explanation: The propagation constant is a complex quantity. It is given by γ = α + jβ, where α is the attenuation constant, a real value and β is the phase constant, a complex value.

5. Calculate the propagation constant of a wave with impedance and admittance given by 32 and 12 respectively.
a) 19.6
b) 17.6
c) 15.6
d) 13.6

Explanation: The propagation constant is given by γ = √(ZY), where Z is the impedance and Y is the admittance. On substituting for Z = 32 and Y = 12, we get γ = 19.6 units.
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6. The intrinsic angle is 250, find the loss angle.
a) 12.5
b) 50
c) 25
d) 75

Explanation: The loss angle is twice of the intrinsic angle. It is given by δ = 2θn. On substituting for θn = 25, the loss angle δ = 2(25) = 50 degree.

7. The standing wave ratio of the wave with maximum and minimum electric field intensities of 12 and 4 is
a) 12
b) 4
c) 3
d) 48

Explanation: The SWR is defined as the ratio of maximum electric field intensities to the minimum field intensities. It is given by S = EMAX/EMIN. Thus for the given data, S = 12/4 = 3.

8. The standing wave ratio of a wave travelling through two media having intrinsic impedances of 3 and 2 is
a) 23
b) 32
c) 15
d) 5

Explanation: The standing wave ratio is given by the ratio of the intrinsic impedance of medium 1 to the intrinsic impedance of medium 2. Thus S = η1/η2. On substituting for η1 = 3 and η2 = 2, we get S = 3/2.

9. The reflection coefficient of a wave travelling through two media having electric intrinsic impedances of 3 and 5 respectively is
a) 2
b) 8
c) 53
d) 1/4

Explanation: The reflection coefficient in terms for intrinsic impedance is R= η2-η1/η2+η1. On substituting the given data, we get R = 5 – 3/5 + 3 = 2/8 = ¼.

10. The reflection coefficient of a wave travelling through two media having magnetic intrinsic impedances of 2 and 1 respectively is
a) 12
b) 13
c) 14
d) 15

Explanation: The reflection coefficient in terms for magnetic intrinsic impedance is R = η1 – η2/η1 + η2. On substituting the given data, we get R = 2 – 1/2 + 1 = 1/3.

11. The transmission coefficient of a wave travelling through two media having electric intrinsic impedances of 3 and 2 respectively is
a) 22
b) 89
c) 45
d) 14

Explanation: The transmission coefficient in terms for intrinsic impedance is R = 2η2/η2 + η1. On substituting the given data, we get R = 2 x 2/2 + 3 = 4/5.

12. The transmission coefficient of a wave travelling through two media having electric intrinsic impedances of 3 and 4 respectively is
a) 23
b) 89
c) 25
d) 67

Explanation: The transmission coefficient in terms for intrinsic impedance is R = 2η1/η2 + η1. On substituting the given data, we get R = 2 x 34 + 3 = 6/7.

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