Jkp Constable Telecommunication Telecommunication Mcqs Jkp Constable (1089 MCQs) | JKSSB & SSC Quiz

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Practice Questions

1089 Total
Question 31 Discuss
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An optical fiber has a core refractive index of 1.5 and a cladding refractive index of 1.2. Calculate its Numerical Aperture.

A
0.3
B
0.9
C
0.81
D
0.27

Answer & Explanation

Correct Option: B

NA = sqrt(n1^2 - n2^2) = sqrt(1.5^2 - 1.2^2) = sqrt(2.25 - 1.44) = sqrt(0.81) = 0.9.
Question 32 Discuss
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The efficiency of an SMPS (Switched-Mode Power Supply) is typically higher than a linear power supply because:

A
It uses a larger transformer
B
The series transistor operates in active region
C
The regulating transistor operates either fully ON or fully OFF
D
It lacks a feedback loop

Answer & Explanation

Correct Option: C

In an SMPS, switching transistors act as switches (cutoff or saturation), minimizing power dissipation compared to the active region operation of linear regulators.
Question 33 Discuss
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What is the primary difference between an Online UPS and an Offline UPS?

A
Online UPS runs only on DC power
B
Offline UPS has zero transfer time
C
Online UPS supplies power constantly from the inverter
D
Online UPS lacks a battery

Answer & Explanation

Correct Option: C

In an Online UPS, the load is always powered by the inverter (AC-DC-AC conversion), resulting in zero transfer time during a power failure.
Question 34 Discuss
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Which type of waveform is produced by the most basic square-wave inverter without filtering?

A
Pure sine wave
B
Square wave rich in odd harmonics
C
Sawtooth wave
D
Triangular wave

Answer & Explanation

Correct Option: B

Basic inverters switch polarity abruptly, generating a square wave that contains the fundamental frequency and numerous odd harmonics.
Question 35 Discuss
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How does an Automatic Voltage Stabilizer regulate output voltage during a severe input voltage drop?

A
By increasing the frequency
B
By engaging the buck operation of an autotransformer
C
By engaging the boost operation of an autotransformer
D
By converting AC to pure DC

Answer & Explanation

Correct Option: C

During low input voltage, relays switch transformer taps to add voltage (boost mode). High voltage triggers subtraction (buck mode).
Question 36 Discuss
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In a CRT television receiver, the deflection coils are driven by which type of waveform?

A
Sine wave
B
Square wave
C
Sawtooth wave
D
Pulse wave

Answer & Explanation

Correct Option: C

A sawtooth current waveform is required to move the electron beam linearly across the screen and rapidly return it (retrace).
Question 37 Discuss
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The ability of a radio receiver to reject unwanted signals operating on adjacent frequencies is known as:

A
Sensitivity
B
Fidelity
C
Selectivity
D
Stability

Answer & Explanation

Correct Option: C

Selectivity measures how well a receiver distinguishes the desired signal from neighboring frequencies, largely determined by the IF stages.
Question 38 Discuss
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Modal dispersion is a significant limiting factor primarily in which type of optical fiber?

A
Single-mode step-index fiber
B
Multimode step-index fiber
C
Multimode graded-index fiber
D
Plastic optical fiber

Answer & Explanation

Correct Option: B

In multimode step-index fibers, different light modes travel different distances, causing severe pulse broadening (modal dispersion).
Question 39 Discuss
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A double conversion superheterodyne receiver is designed to specifically improve:

A
Audio fidelity
B
Image rejection
C
Power efficiency
D
FM threshold effect

Answer & Explanation

Correct Option: B

Using a high first IF pushes the image frequency further away, improving image rejection, while a low second IF provides high selectivity.
Question 40 Discuss
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In modern inverters, what technique is widely used to synthesize a sine wave output and reduce harmonic distortion?

A
Pulse Code Modulation (PCM)
B
Pulse Width Modulation (PWM)
C
Frequency Modulation (FM)
D
Phase Shift Keying (PSK)

Answer & Explanation

Correct Option: B

PWM rapidly switches the inverter's transistors, varying the pulse width to closely approximate a clean sine wave when filtered.
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