# Electromagnetic Theory Questions and Answers – Types of Transmission Lines

This set of Electromagnetic Theory Multiple Choice Questions & Answers (MCQs) focuses on “Types of Transmission Lines”.

1. Identify which of the following is not a transmission line?
a) Telephone lines
b) Power transmission
c) Underground cables
d) Cavity resonators

Explanation: The types of transmission line are telephone lines, power transmission lines, underground cables, coaxial cables, fibre optic cable transmission etc. Cavity resonators are not transmission lines, they are components that aid maximum transmission.

2. The open wire transmission line consists of
a) Conductor
b) Dielectric
c) Both conductor and dielectric
d) Either conductor or dielectric

Explanation: The open wire is a common form of transmission line. The open wire consists of conductors. The conductors of such lines are considered to be parallel and separated by a dielectric.

3. Telephone lines and power lines are open wire transmission lines. State true/false.
a) True
b) False

Explanation: The open wire lines are long and used for distant wired communication. Such lines are telephone and power lines.

4. The cable transmission line consists of
a) Conductors
b) Insulators
c) Insulated conductors
d) Insulated conductors with dielectric

Explanation: The cable lines are underground transmission lines. The line consists of hundreds of individual paper insulated conductors twisted in pairs and combined inside a protective lead or plastic sheath, which is usually a solid dielectric.

5. The conductors lie perpendicularly with the dielectric in the cable line. State true/false.
a) True
b) False

Explanation: In all the transmission lines, the conductors are considered to be parallel with a solid dielectric.
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6. The coaxial cable consists of
a) Conductors
b) Dielectric
c) Conductor with dielectric
d) Two conductors with dielectric

Explanation: The coaxial cable consists of a hollow conductor and the second conductor is located inside and coaxial with the tube. The dielectric may be solid or gaseous.

7. The coaxial cable are used in
a) Telephone cables transmission
b) Power transmission
c) Television signal transmission
d) Short wave transmission

Explanation: Practically, the coaxial cables are employed in the transmission of the television signals from the dish antenna to the transponder.

8. Identify which is not a type of waveguide.
a) Rectangular
b) Circular
c) Cylindrical
d) Cavity resonator

Explanation: Rectangular waveguide is a commonly used waveguide. Cylindrical and circular waveguides are the same. Cavity resonator is not a waveguide.

9. The range of frequencies handled by the waveguides is in
a) Hz
b) KHz
c) MHz
d) GHz

Explanation: The waveguides are operated in the GHz range. In particular, the waveguides are active above 6 GHz. The range goes upto several tens of GHz. Beyond this range, the transmission is handled by optic fibre cables.

10. The range of frequencies operated by the coaxial cables is in
a) Hz
b) kHz
c) MHz
d) GHz

Explanation: Coaxial cables are operated in the MHz range. The main application includes television cable line transmission.

11. The cut off frequency for waveguide operation is
a) 2 MHz
b) 6 GHz
c) 4 MHz
d) 6 MHz

Explanation: The waveguides should be operated above the cut off frequency of 6 GHz. This will lead to effective power transmission. At a frequency below this, will lead to attenuation.

12. The highest means of communication is
a) Internet
b) Telephone
c) Television

Explanation: Though all the means of communication use the radio frequencies, the internet communication is the fastest. It involves email, voice message, video message etc. The telephone, television and radio use transmission lines for communication through radio frequencies, whereas the internet uses both wired and wireless means. Also it employs optic fibre, which uses light as the medium, since it is faster than the radio signals.

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