Q.1 Which of the following is a primary function of a communication system?
To amplify sound only
To transmit information from sender to receiver
To convert mechanical energy to electrical energy
To store data permanently
Explanation - The main purpose of a communication system is to transmit information from a sender to a receiver efficiently.
Correct answer is: To transmit information from sender to receiver
Q.2 Which type of modulation varies the amplitude of the carrier signal?
Frequency Modulation (FM)
Phase Modulation (PM)
Amplitude Modulation (AM)
Pulse Code Modulation (PCM)
Explanation - In Amplitude Modulation (AM), the amplitude of the carrier signal is varied in accordance with the message signal.
Correct answer is: Amplitude Modulation (AM)
Q.3 In frequency modulation (FM), which property of the carrier changes?
Amplitude
Frequency
Phase
All of the above
Explanation - In FM, the frequency of the carrier wave varies in proportion to the instantaneous amplitude of the modulating signal, while amplitude remains constant.
Correct answer is: Frequency
Q.4 Which of the following is an example of analog communication?
Radio broadcasting
Digital television
Fiber optic internet
Email transmission
Explanation - Radio broadcasting uses continuous signals to transmit information, which is characteristic of analog communication.
Correct answer is: Radio broadcasting
Q.5 Which device is used to convert sound signals into electrical signals?
Speaker
Microphone
Antenna
Transmitter
Explanation - A microphone converts acoustic sound waves into corresponding electrical signals for transmission.
Correct answer is: Microphone
Q.6 Which communication system uses light to transmit information over long distances?
Radio communication
Microwave communication
Optical fiber communication
Satellite communication
Explanation - Optical fiber communication uses light pulses to transmit information, enabling high-speed data transfer over long distances.
Correct answer is: Optical fiber communication
Q.7 Which of the following is used as a modulator in analog communication?
Transistor
Diode
Operational amplifier
All of the above
Explanation - Transistors, diodes, and operational amplifiers can be used in modulation circuits to implement AM, FM, or other analog modulation schemes.
Correct answer is: All of the above
Q.8 The range of frequencies for human hearing is approximately:
20 Hz – 20 kHz
2 Hz – 200 Hz
200 Hz – 2 kHz
20 kHz – 200 kHz
Explanation - Human ears can typically hear frequencies in the range of 20 Hz to 20 kHz, which is important in designing audio communication systems.
Correct answer is: 20 Hz – 20 kHz
Q.9 In digital communication, which technique converts analog signals into digital signals?
Amplitude modulation
Pulse Code Modulation (PCM)
Frequency modulation
Phase modulation
Explanation - Pulse Code Modulation (PCM) is used to convert analog signals into digital form by sampling and quantization.
Correct answer is: Pulse Code Modulation (PCM)
Q.10 Which of the following is a disadvantage of amplitude modulation (AM)?
Susceptibility to noise
High bandwidth requirement
Complex receiver design
Low power consumption
Explanation - AM signals are more affected by noise and interference because noise directly affects the amplitude of the signal.
Correct answer is: Susceptibility to noise
Q.11 What is the main advantage of frequency modulation (FM) over amplitude modulation (AM)?
Requires less bandwidth
Less susceptible to noise
Simpler transmitter
Easier to demodulate
Explanation - FM is less affected by amplitude noise, making it more suitable for high-fidelity audio transmission.
Correct answer is: Less susceptible to noise
Q.12 In a communication system, what is the function of a repeater?
Convert analog signals to digital
Boost signal strength for long-distance transmission
Filter out noise
Encode the message
Explanation - Repeaters amplify and regenerate signals to overcome attenuation in long-distance transmission.
Correct answer is: Boost signal strength for long-distance transmission
Q.13 Which communication system component transmits the signal through a medium?
Transmitter
Receiver
Modulator
Demodulator
Explanation - The transmitter sends the modulated signal through the communication channel to the receiver.
Correct answer is: Transmitter
Q.14 What is the carrier wave in communication systems?
A low-frequency signal containing information
A high-frequency signal used to carry information
Noise signal
A digital pulse
Explanation - A carrier wave is a high-frequency signal modulated by the message signal to facilitate transmission over the channel.
Correct answer is: A high-frequency signal used to carry information
Q.15 Which of the following is true for pulse modulation?
Information is transmitted as continuous waves
Information is transmitted in pulses
Only analog signals can be used
It is unaffected by noise
Explanation - Pulse modulation transmits information by varying properties of pulses, such as amplitude, width, or position.
Correct answer is: Information is transmitted in pulses
Q.16 Which frequency band is typically used for satellite communication?
LF (30-300 kHz)
MF (300 kHz – 3 MHz)
SHF (3-30 GHz)
VLF (3-30 kHz)
Explanation - Satellite communication uses Super High Frequency (SHF) bands for reliable transmission over long distances.
Correct answer is: SHF (3-30 GHz)
Q.17 Which of the following is a method to reduce noise in communication systems?
Using FM instead of AM
Increasing transmitter power only
Decreasing bandwidth
Using an antenna with smaller gain
Explanation - FM is less susceptible to amplitude noise, which helps in reducing the effect of noise in the communication system.
Correct answer is: Using FM instead of AM
Q.18 The speed of signal propagation in an optical fiber is approximately:
Speed of light in vacuum
Half the speed of light
Speed of sound in air
10 times the speed of light
Explanation - Light travels slower in optical fiber than in vacuum due to the refractive index of the fiber, typically around 2/3 the speed of light in vacuum.
Correct answer is: Half the speed of light
Q.19 Which of the following is used for short-range wireless communication?
Bluetooth
Satellite links
AM radio
Fiber optic cables
Explanation - Bluetooth is designed for short-range communication, typically a few meters, suitable for devices like headphones and smartphones.
Correct answer is: Bluetooth
Q.20 Multiplexing is used to:
Increase the noise in a channel
Send multiple signals over a single communication channel
Convert analog signals to digital
Amplify a signal
Explanation - Multiplexing allows multiple signals to share a single channel, increasing efficiency of communication.
Correct answer is: Send multiple signals over a single communication channel
Q.21 Which of the following is true for digital signals compared to analog signals?
More susceptible to noise
Easier to store and process
Cannot be transmitted over long distances
Always uses less bandwidth
Explanation - Digital signals are easier to store, process, and reproduce with less degradation compared to analog signals.
Correct answer is: Easier to store and process
Q.22 Which of the following antennas is typically used for satellite communication?
Yagi-Uda antenna
Parabolic dish antenna
Dipole antenna
Loop antenna
Explanation - Parabolic dish antennas are used for satellite communication because they can focus signals to a narrow beam, achieving long-distance transmission.
Correct answer is: Parabolic dish antenna
Q.23 In phase modulation (PM), which property of the carrier is varied?
Amplitude
Frequency
Phase
None
Explanation - Phase modulation varies the phase of the carrier wave in accordance with the instantaneous amplitude of the message signal.
Correct answer is: Phase
Q.24 Which is the main advantage of using fiber optic communication over copper cables?
Lower bandwidth
Higher attenuation
Less signal loss and higher data rates
More susceptibility to electromagnetic interference
Explanation - Fiber optic cables offer higher bandwidth, minimal signal loss, and immunity to electromagnetic interference compared to copper cables.
Correct answer is: Less signal loss and higher data rates