250+ TOP MCQs on Power Calculation and Answers

Analog Communications Multiple Choice Questions focuses on “Power Calculation”.

1. If peak voltage of a carrier wave is 10V, what is the peak voltage of modulating signal if modulation index is 50%?
a) 10V
b) 20V
c) 8V
d) 5V
Answer: d
Clarification: From the relation, Modulation Index (µ) = V_m/V_c = 50% = 0.5,
where V_m = Peak voltage of modulating signal,
V_c = Peak voltage of a carrier wave = 10V,
Therefore, V_m = 10 X 0.5 = 5V.

2. Maximum Amplitude of an amplitude modulated 10V and minimum amplitude is 5V. Find its modulation index?
a) 0.65
b) 0.9
c) 0.33
d) 1
Answer: c
Clarification: We know, Modulation Index(µ) = (V_max-V_min)/(V_max+V_min),
Where, V_max = Maximum Amplitude of an amplitude modulated = 10V
V_min = Minimum amplitude of an amplitude modulated = 5V
Therefore, µ = (10-5)/(10+5) = 0.33.

3. 24 channels, each band limited to 3.4 KHz, are to be time division multiplexed. Find the bandwidth required for 128 quantization level? (Given that sampling frequency is 8 KHz)
a) 2436 KHz
b) 1002 KHz
c) 1536 KHz
d) 1337 KHz
Answer: c
Clarification: N = 24, f_m = 3.4 kHz
m = 128,
2ⁿ = m = 128, n = 7
But f_s = 2f_m, where, f_s = sampling frequency
instead at 2f_m 2 x 3.4 kHz 6.8 KHz.
B.W. = N(n+1)X f_s = [24(7 + 1)] 8 kHz = 1536 KHz.

4. Sampling frequency of a signal is 6 KHz and is quantized using 7 bit quantizer. Find its bit rate?
a) 48kbPs
b) 64kbPs
c) 16kbPs
d) 8kbPs
Answer: a
Clarification: Bit rate refers to the rate at which data is processed or transferred. It is usually measured in seconds, ranging from bps for smaller values to kbps and mbps.
Bit rate is also known as bitrate or data rate.
Bit rate, R_b = ¹⁄_Tb where where n = number of bits and f_s = Sampling Frequency
T_b = 1/42, therefore Bit rate = 42 Kbps.