JEE Physics Communication System MCQs Set 07

Download JEE MCQs for JEE Physics: Communication System

Access targeted multiple-choice questions for Communication System designed to align with the latest JEE academic syllabus for JEE Physics. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.

Chapter-wise Objective Questions: Communication System

View or download the dedicated Communication System MCQ resource below. Practicing these 50 objective questions regularly builds familiarity with standard exam patterns and helps secure higher marks in final Physics evaluations.

Multiple Choice Questions

Question 1: Choose the correct statement.
(a) In amplitude modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal
(b) In amplitude modulation the frequency of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal
(c) In frequency modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal
(d) In frequency modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the frequency of the audio signal
Show Answer & Explanation

Answer: (a) In amplitude modulation the amplitude of the high frequency carrier wave is made to vary in proportion to the amplitude of the audio signal

Explanation:
1. AM varies the carrier amplitude with the signal amplitude; FM varies the carrier frequency with the signal amplitude.
2. Only the first statement is correct.

Teacher's Note:
1. Modulation varies one property of the carrier in step with the message.

Question 2: An audio signal consists of two distinct sounds: one is a human speech signal in the frequency band of 200 Hz to 2700 Hz, the other is a high frequency music signal in the band of 10200 Hz to 15200 Hz. The ratio of the AM signal bandwidth required to send both signals together (a band from 200 Hz to 15200 Hz) to the AM bandwidth required to send just the human speech is:
(a) 2
(b) 5
(c) 6
(d) 3
Show Answer & Explanation

Answer: (c) 6

Explanation:
1. AM bandwidth is twice the signal band: speech \( 2\times(2700-200)=5000\ \text{Hz} \); both \( 2\times(15200-200)=30000\ \text{Hz} \).
2. Ratio \( \frac{30000}{5000}=6 \)

Teacher's Note:
1. AM bandwidth is twice the width of the message band.

Question 3: A modulated signal has the form \( C_m(t)=30\sin300\pi t+10(\cos200\pi t-\cos400\pi t) \). The carrier frequency \( f_c \), the modulating frequency \( f_m \) and the modulation index \( \mu \) are respectively:
(a) \( f_c=200\ \text{Hz};f_m=50\ \text{Hz};\mu=\frac12 \)
(b) \( f_c=150\ \text{Hz};f_m=50\ \text{Hz};\mu=\frac23 \)
(c) \( f_c=150\ \text{Hz};f_m=30\ \text{Hz};\mu=\frac13 \)
(d) \( f_c=200\ \text{Hz};f_m=30\ \text{Hz};\mu=\frac12 \)
Show Answer & Explanation

Answer: (b) \( f_c=150\ \text{Hz};f_m=50\ \text{Hz};\mu=\frac23 \)

Explanation:
1. Carrier term: \( 300\pi t\Rightarrow f_c=150\ \text{Hz} \), amplitude 30. Side bands at \( 100 \) and \( 200 \) Hz, each of amplitude 10.
2. Side band spacing: \( f_m=\frac{200-100}{2}=50\ \text{Hz} \). Each side band has amplitude \( \frac{\mu A_c}2=10\Rightarrow\mu=\frac{20}{30}=\frac23 \)

Teacher's Note:
1. Sidebands lie at fc plus and minus fm, each with amplitude mu Ac over 2.

Question 4: A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. The frequencies of the resultant signal are:
(a) 2005 kHz, 2000 kHz and 1995 kHz
(b) 2000 kHz and 1995 kHz
(c) 2 MHz only
(d) 2005 kHz and 1995 kHz
Show Answer & Explanation

Answer: (a) 2005 kHz, 2000 kHz and 1995 kHz

Explanation:
1. AM output contains the carrier and two side bands: \( f_c\pm f_m=2000\pm5 \) kHz, i.e. 2005, 2000 and 1995 kHz.

Teacher's Note:
1. An amplitude modulated wave has the carrier and the upper and lower side bands.

Question 5: A 1 kW signal is transmitted using a communication channel that provides attenuation at the rate of -2 dB per km. If the communication channel has a total length of 5 km, the power of the signal received is (gain in dB \( =10\log\frac{P_0}{P_i} \)):
(a) 900 W
(b) 100 W
(c) 990 W
(d) 1010 W
Show Answer & Explanation

Answer: (b) 100 W

Explanation:
1. Total attenuation \( =-2\times5=-10\ \text{dB} \).
2. \( 10\log\frac{P_0}{1000}=-10\Rightarrow P_0=100\ \text{W} \)

Teacher's Note:
1. A change of -10 dB reduces the power to one tenth.

Question 6: Current-voltage characteristics of four devices are: (i) a straight line through the origin, (ii) a curve rising exponentially for positive voltage (diode like), (iii) a constant current independent of voltage, (iv) a curve with an initial sharp rise, a flat region and then a further rise. Identify the devices that can be used for modulation:
(a) (i) and (iii)
(b) Only (iii)
(c) (ii) and some regions of (iv)
(d) All the devices can be used
Show Answer & Explanation

Answer: (c) (ii) and some regions of (iv)

Explanation:
1. Modulation needs a non-linear device, because a linear one only scales the input and generates no new frequencies.
2. Devices (ii) and the non-linear regions of (iv) qualify.

Teacher's Note:
1. Frequency mixing requires a non-linear element.

Question 7: A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due to:
(a) Poor selection of modulation index (selected 0 < m < 1)
(b) Poor bandwidth selection of amplifiers
(c) Poor selection of carrier frequency
(d) Loss of energy in transmission
Show Answer & Explanation

Answer: (b) Poor bandwidth selection of amplifiers

Explanation:
1. If the amplifiers pass only the higher part of the voice frequency band, the low frequencies of a male voice are lost and the voice sounds higher pitched.
2. The modulation index in the range 0 to 1 is correct and does not change the pitch.

Teacher's Note:
1. Insufficient amplifier bandwidth cuts the low frequency components.

Question 8: A basic communication system consists of: (a) transmitter, (b) information source, (c) user of information, (d) channel, (e) receiver. The correct sequence in which these are arranged in a basic communication system is:
(a) (a), (b), (d), (e), (c)
(b) (b), (a), (d), (e), (c)
(c) (b), (d), (a), (c), (e)
(d) (b), (e), (a), (d), (c)
Show Answer & Explanation

Answer: (b) (b), (a), (d), (e), (c)

Explanation:
1. The information source feeds the transmitter, the signal goes through the channel to the receiver, which delivers it to the user: source, transmitter, channel, receiver, user.

Teacher's Note:
1. Follow the signal path from source to user.

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Practice MCQs for JEE Physics Communication System

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FAQs

Where can I access latest JEE Physics Communication System MCQs Set 07?

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Are Assertion-Reasoning and Case-Study MCQs included in the Physics JEE material?

Yes, our JEE Physics Communication System MCQs Set 07 include the latest type of questions, such as Assertion-Reasoning and Case-based MCQs. 50% of the JEE paper is now competency-based.

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By solving our JEE Physics Communication System MCQs Set 07, JEE students can improve their accuracy and speed which is important as objective questions provide a chance to secure 100% marks in the Physics.

Do you provide answers and explanations for JEE Physics Communication System MCQs Set 07?

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