Test: Types of Waveguides & Its Properties
20 Questions MCQ Test Electromagnetic Fields Theory (EMFT) | Test: Types of Waveguides & Its Properties
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The phenomenon employed in the waveguide operation is
Answer: c
Explanation: The waveguides use total internal reflection phenomenon to transmit the waves passing through it. Thus the acceptance angle and critical angle are important for effective transmission.
The dominant mode in waveguide is the mode which has
Answer: b
Explanation: The dominant mode is the mode which has the minimum frequency or maximum wavelength available for propagation of the waves
The modes are calculated from which parameter?
Answer: d
Explanation: The modes are calculated from the V number of the waveguides. It is given by M= V2/2.
The circular waveguides use which function in the frequency calculation?
Answer: c
Explanation: The circular or cylindrical waveguides use the Bessel function for the frequency calculation of a particular mode.
The scattering parameters are used to indicate the
Answer: c
Explanation: The scattering matrix consists of the transmission coefficients in the main diagonal and the reflection coefficients in the opposite diagonal.
Which of the following two parameter models cannot be used to represent a transmission line?
Answer: a
Explanation: The T, ABCD and S parameter models are used in the transmission line modelling. The h parameter is not used for the same.
For the matched line, the parameters S12 and S21 are
Answer: b
Explanation: The parameters S12 and S21 are the reflection coefficients. For a matched line, the reflection coefficients are zero. Thus the parameters S12 and S21 are also zero.
The waveguides are materials with characteristics of
Answer: a
Explanation: Generally, the waveguides are made of materials with low bulk resistivity like brass, copper, silver etc. But if the interior walls are properly plated, it is possible with poor conductivity materials too. It is even possible to make plastic waveguides.
The parameters S11 and S22 indicate the transmission coefficients. State true/false.
Answer: a
Explanation: In a scattering matrix, the parameters S11 and S22 indicate the transmission coefficients and the parameters S21 and S12 indicate the reflection coefficients.
The waveguides increase the transmission of the electromagnetic waves. State true/false.
Answer: a
Explanation: The waveguides aid in effective transmission of the electromagnetic power from the source antenna to the destination antenna.
The waveguide is employed in the transmission lines, when operated at the range of
Answer: d
Explanation: Waveguides are employed for effective transmission, when the lines carry electromagnetic waves in the GHz range.
The cut off frequency for a waveguide to operate is
Answer: d
Explanation: The cut off frequency of the waveguide is 6 GHz. This is the frequency at which the waveguide will start to operate.
In rectangular waveguides, the dimensions a and b represent the
Answer: b
Explanation: In rectangular waveguide, the a parameter is the broad wall dimension of the waveguide and the b parameter is the side wall dimension of the waveguide. Always, a > b in a waveguide.
Answer: a
Explanation: The Bessel function is used in the circular waveguides. Normally Jn(ha) = 0. Here n is the order of the Bessel function.
In a waveguide, always which condition holds good?
Answer: b
Explanation: In air medium, the phase velocity is assumed to be the speed of light. For waveguides, the phase velocity is always greater than the speed of the light.
The group wavelength is greater than the wavelength at any point. State true/false.
Answer: a
Explanation: In a waveguide, the phase velocity is greater than the velocity of light. Thus the group velocity will be less. This implies the group wavelength will be greater than the wavelength at any point.
Find the group wavelength of a wave, given that the group phase constant is 6.28 units.
Answer: d
Explanation: The group wavelength is given by λg = 2π/βg, where βg is the group wavelength of the wave. On substituting for βg = 6.28, we get group wavelength as unity.
The phase velocity of a wave with frequency of 15 radian/sec and group phase constant of 2 units is
Answer: c
Explanation: The phase velocity of a wave is given by Vp = ω/βg. on substituting for ω = 15 and βg = 2, we get phase velocity as 15/2 = 7.5 units.
The modes in a material having a V number of 20 is
Answer: c
Explanation: The relation between the modes and the V number is given by m = v2/2. Given that v = 20, we get m = 202/2 = 200 modes
The number of modes is given as 50, find the V number.
Answer: b
Explanation: The relation between the modes and the V number is given by m = v2/2. Given that m = 50, we get v2 = 2 x 50 = 100. The V number is 10.
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