1 Only amplitude is change, but frequency, phase remains constant
2 Frequency, phase are change, but Amplitude remains constant
3 Amplitude, Frequency are constant but phase change
4 Amplitude, Phase are constant but frequency changes
Explanation:
Conceptual Question
PHXII15:COMMUNICATION SYSTEMS
356757
Assertion : A portable AM radio set must be kept horizontal to receive the signals properly. Reason : Radio waves are polarised electromagnetic waves.
1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.
2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.
3 Assertion is correct but Reason is incorrect.
4 Assertion is incorrect but reason is correct.
Explanation:
It is true that the radiowaves are polarised electromagnetic waves. The antenna of portable AM radio is sensitive to only magnetic components of electromagnetic waves. On account of this the set should be put horizontal and in proper situation so that the signals are received properly from radio station.
PHXII15:COMMUNICATION SYSTEMS
356758
A single frequency \(20kHz\) and peak voltage of 5 volt is used to modulate a carrier wave of frequency \(1.2MHz\) and peak voltage 25 volts. Choose the correct statement.
1 Modulation index \(=5\), side frequency bands are at \(1400kHz\,\,{\rm{and}}\,\,1000kHz\)
2 Modulation index \(=0.8\), side frequency bands are at \(1180kHz\,\,{\rm{and}}\,\,1220kHz\)
3 Modulation index \(=0.2\), side frequency bands are at \(1220kHz\,\,{\rm{and}}\,\,1180kHz\)
4 Modulation index \(=5\), side frequency bands are at \(21/2kHz\,\,{\rm{and}}\,\,18.8kHz\)
Explanation:
Modulation index \(=m=\dfrac{V_{m}}{V_{0}}=\dfrac{1}{5}=0.2\) Frequency \(=12 \times 10^{3} \mathrm{kHz}\) \(\begin{aligned}& F=12.00 \mathrm{kHz} \\& F_{1}=1200-20=1180 \mathrm{kHz} \\& F_{2}=1200+20=1220 \mathrm{kHz}\end{aligned}\)
JEE - 2017
PHXII15:COMMUNICATION SYSTEMS
356759
A diode detector is used to detect an amplitude modulated wave of \(60 \%\) modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance of 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.
1 \(10.62MHz\)
2 \(10.62kHz\)
3 \(5.31MHz\)
4 \(5.31kHz\)
Explanation:
\(\tau=R C=100 \times 10^{3} \times 250 \times 10^{-12} \mathrm{sec}\) \(\begin{aligned}& =2.5 \times 10^{7} \times 10^{-12} \mathrm{sec} \\& =2.5 \times 10^{-5} \mathrm{sec}\end{aligned}\) The higher frequency which can be detected with tolerable distortion is \(f = \frac{1}{{2\pi {m_a}RC}} = \frac{1}{{2\pi \times 0.6 \times 2.5 \times {{10}^{ - 5}}}}Hz\) \( = \frac{{100 \times {{10}^4}}}{{25 \times 1.2\pi }}Hz = \frac{4}{{1.2\pi }} \times {10^{ - 4}}\;Hz\) \( = 10.61KHz\) This condition is obtained by applying the condition that rate of decay of capacitor voltage must be equal or less than the rate of decay of modulated signal voltage for proper detection of modulated signal.
1 Only amplitude is change, but frequency, phase remains constant
2 Frequency, phase are change, but Amplitude remains constant
3 Amplitude, Frequency are constant but phase change
4 Amplitude, Phase are constant but frequency changes
Explanation:
Conceptual Question
PHXII15:COMMUNICATION SYSTEMS
356757
Assertion : A portable AM radio set must be kept horizontal to receive the signals properly. Reason : Radio waves are polarised electromagnetic waves.
1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.
2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.
3 Assertion is correct but Reason is incorrect.
4 Assertion is incorrect but reason is correct.
Explanation:
It is true that the radiowaves are polarised electromagnetic waves. The antenna of portable AM radio is sensitive to only magnetic components of electromagnetic waves. On account of this the set should be put horizontal and in proper situation so that the signals are received properly from radio station.
PHXII15:COMMUNICATION SYSTEMS
356758
A single frequency \(20kHz\) and peak voltage of 5 volt is used to modulate a carrier wave of frequency \(1.2MHz\) and peak voltage 25 volts. Choose the correct statement.
1 Modulation index \(=5\), side frequency bands are at \(1400kHz\,\,{\rm{and}}\,\,1000kHz\)
2 Modulation index \(=0.8\), side frequency bands are at \(1180kHz\,\,{\rm{and}}\,\,1220kHz\)
3 Modulation index \(=0.2\), side frequency bands are at \(1220kHz\,\,{\rm{and}}\,\,1180kHz\)
4 Modulation index \(=5\), side frequency bands are at \(21/2kHz\,\,{\rm{and}}\,\,18.8kHz\)
Explanation:
Modulation index \(=m=\dfrac{V_{m}}{V_{0}}=\dfrac{1}{5}=0.2\) Frequency \(=12 \times 10^{3} \mathrm{kHz}\) \(\begin{aligned}& F=12.00 \mathrm{kHz} \\& F_{1}=1200-20=1180 \mathrm{kHz} \\& F_{2}=1200+20=1220 \mathrm{kHz}\end{aligned}\)
JEE - 2017
PHXII15:COMMUNICATION SYSTEMS
356759
A diode detector is used to detect an amplitude modulated wave of \(60 \%\) modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance of 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.
1 \(10.62MHz\)
2 \(10.62kHz\)
3 \(5.31MHz\)
4 \(5.31kHz\)
Explanation:
\(\tau=R C=100 \times 10^{3} \times 250 \times 10^{-12} \mathrm{sec}\) \(\begin{aligned}& =2.5 \times 10^{7} \times 10^{-12} \mathrm{sec} \\& =2.5 \times 10^{-5} \mathrm{sec}\end{aligned}\) The higher frequency which can be detected with tolerable distortion is \(f = \frac{1}{{2\pi {m_a}RC}} = \frac{1}{{2\pi \times 0.6 \times 2.5 \times {{10}^{ - 5}}}}Hz\) \( = \frac{{100 \times {{10}^4}}}{{25 \times 1.2\pi }}Hz = \frac{4}{{1.2\pi }} \times {10^{ - 4}}\;Hz\) \( = 10.61KHz\) This condition is obtained by applying the condition that rate of decay of capacitor voltage must be equal or less than the rate of decay of modulated signal voltage for proper detection of modulated signal.
1 Only amplitude is change, but frequency, phase remains constant
2 Frequency, phase are change, but Amplitude remains constant
3 Amplitude, Frequency are constant but phase change
4 Amplitude, Phase are constant but frequency changes
Explanation:
Conceptual Question
PHXII15:COMMUNICATION SYSTEMS
356757
Assertion : A portable AM radio set must be kept horizontal to receive the signals properly. Reason : Radio waves are polarised electromagnetic waves.
1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.
2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.
3 Assertion is correct but Reason is incorrect.
4 Assertion is incorrect but reason is correct.
Explanation:
It is true that the radiowaves are polarised electromagnetic waves. The antenna of portable AM radio is sensitive to only magnetic components of electromagnetic waves. On account of this the set should be put horizontal and in proper situation so that the signals are received properly from radio station.
PHXII15:COMMUNICATION SYSTEMS
356758
A single frequency \(20kHz\) and peak voltage of 5 volt is used to modulate a carrier wave of frequency \(1.2MHz\) and peak voltage 25 volts. Choose the correct statement.
1 Modulation index \(=5\), side frequency bands are at \(1400kHz\,\,{\rm{and}}\,\,1000kHz\)
2 Modulation index \(=0.8\), side frequency bands are at \(1180kHz\,\,{\rm{and}}\,\,1220kHz\)
3 Modulation index \(=0.2\), side frequency bands are at \(1220kHz\,\,{\rm{and}}\,\,1180kHz\)
4 Modulation index \(=5\), side frequency bands are at \(21/2kHz\,\,{\rm{and}}\,\,18.8kHz\)
Explanation:
Modulation index \(=m=\dfrac{V_{m}}{V_{0}}=\dfrac{1}{5}=0.2\) Frequency \(=12 \times 10^{3} \mathrm{kHz}\) \(\begin{aligned}& F=12.00 \mathrm{kHz} \\& F_{1}=1200-20=1180 \mathrm{kHz} \\& F_{2}=1200+20=1220 \mathrm{kHz}\end{aligned}\)
JEE - 2017
PHXII15:COMMUNICATION SYSTEMS
356759
A diode detector is used to detect an amplitude modulated wave of \(60 \%\) modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance of 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.
1 \(10.62MHz\)
2 \(10.62kHz\)
3 \(5.31MHz\)
4 \(5.31kHz\)
Explanation:
\(\tau=R C=100 \times 10^{3} \times 250 \times 10^{-12} \mathrm{sec}\) \(\begin{aligned}& =2.5 \times 10^{7} \times 10^{-12} \mathrm{sec} \\& =2.5 \times 10^{-5} \mathrm{sec}\end{aligned}\) The higher frequency which can be detected with tolerable distortion is \(f = \frac{1}{{2\pi {m_a}RC}} = \frac{1}{{2\pi \times 0.6 \times 2.5 \times {{10}^{ - 5}}}}Hz\) \( = \frac{{100 \times {{10}^4}}}{{25 \times 1.2\pi }}Hz = \frac{4}{{1.2\pi }} \times {10^{ - 4}}\;Hz\) \( = 10.61KHz\) This condition is obtained by applying the condition that rate of decay of capacitor voltage must be equal or less than the rate of decay of modulated signal voltage for proper detection of modulated signal.
1 Only amplitude is change, but frequency, phase remains constant
2 Frequency, phase are change, but Amplitude remains constant
3 Amplitude, Frequency are constant but phase change
4 Amplitude, Phase are constant but frequency changes
Explanation:
Conceptual Question
PHXII15:COMMUNICATION SYSTEMS
356757
Assertion : A portable AM radio set must be kept horizontal to receive the signals properly. Reason : Radio waves are polarised electromagnetic waves.
1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.
2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.
3 Assertion is correct but Reason is incorrect.
4 Assertion is incorrect but reason is correct.
Explanation:
It is true that the radiowaves are polarised electromagnetic waves. The antenna of portable AM radio is sensitive to only magnetic components of electromagnetic waves. On account of this the set should be put horizontal and in proper situation so that the signals are received properly from radio station.
PHXII15:COMMUNICATION SYSTEMS
356758
A single frequency \(20kHz\) and peak voltage of 5 volt is used to modulate a carrier wave of frequency \(1.2MHz\) and peak voltage 25 volts. Choose the correct statement.
1 Modulation index \(=5\), side frequency bands are at \(1400kHz\,\,{\rm{and}}\,\,1000kHz\)
2 Modulation index \(=0.8\), side frequency bands are at \(1180kHz\,\,{\rm{and}}\,\,1220kHz\)
3 Modulation index \(=0.2\), side frequency bands are at \(1220kHz\,\,{\rm{and}}\,\,1180kHz\)
4 Modulation index \(=5\), side frequency bands are at \(21/2kHz\,\,{\rm{and}}\,\,18.8kHz\)
Explanation:
Modulation index \(=m=\dfrac{V_{m}}{V_{0}}=\dfrac{1}{5}=0.2\) Frequency \(=12 \times 10^{3} \mathrm{kHz}\) \(\begin{aligned}& F=12.00 \mathrm{kHz} \\& F_{1}=1200-20=1180 \mathrm{kHz} \\& F_{2}=1200+20=1220 \mathrm{kHz}\end{aligned}\)
JEE - 2017
PHXII15:COMMUNICATION SYSTEMS
356759
A diode detector is used to detect an amplitude modulated wave of \(60 \%\) modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance of 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.
1 \(10.62MHz\)
2 \(10.62kHz\)
3 \(5.31MHz\)
4 \(5.31kHz\)
Explanation:
\(\tau=R C=100 \times 10^{3} \times 250 \times 10^{-12} \mathrm{sec}\) \(\begin{aligned}& =2.5 \times 10^{7} \times 10^{-12} \mathrm{sec} \\& =2.5 \times 10^{-5} \mathrm{sec}\end{aligned}\) The higher frequency which can be detected with tolerable distortion is \(f = \frac{1}{{2\pi {m_a}RC}} = \frac{1}{{2\pi \times 0.6 \times 2.5 \times {{10}^{ - 5}}}}Hz\) \( = \frac{{100 \times {{10}^4}}}{{25 \times 1.2\pi }}Hz = \frac{4}{{1.2\pi }} \times {10^{ - 4}}\;Hz\) \( = 10.61KHz\) This condition is obtained by applying the condition that rate of decay of capacitor voltage must be equal or less than the rate of decay of modulated signal voltage for proper detection of modulated signal.
