Engineering Questions with Answers - Multiple Choice Questions

MCQs on Fourier Theory

1 - Question

A sine wave whose frequency is some integer multiple of a fundamental sine wave is called?
a) Complex wave
b) Square wave
c) Harmonic
d) Digital pulses

View Answer

c
Explanation: A harmonic is a sine wave whose frequency is some integer multiple of a fundamental sine wave. The third harmonic of a 2-kHz sine wave is a sine wave of 6 kHz.




2 - Question

What is the duty cycle of a square wave with equal duration positive and negative alterations?
a) 100%
b) 50%
c) 200%
d) 25%

View Answer

b
Explanation: Duty cycle is the ratio of the duration of the positive alteration t1 to the period T expressed as percentage. D= t1⁄T*100 = t1⁄2t1 * 100 = 50%.




3 - Question

What is the frequency of 7th harmonic of a 2KHz sine wave?
a) 14Khz
b) 9KHz
c) 5KHz
d) 2KHz

View Answer

a
Explanation: The frequency of 7th harmonic sine wave = 7 x 2KHz = 14KHz




4 - Question

An infinite number of odd harmonics are present in a sine wave.
a) True
b) False

View Answer

a
Explanation: A square wave is made up of a sine wave at the fundamental frequency of the square wave plus an infinite number of odd harmonics. For example, if the fundamental frequency of the square wave is 1 kHz, the square wave can be synthesized by adding the 1-kHz sine wave and harmonic sine waves of 3 kHz, 5 kHz, 7 kHz, 9 kHz, etc.




5 - Question

What is the peak value of 5th harmonic if the square wave has a peak voltage of 3v and a frequency of 48Khz?
a) 0.74
b) 0.52
c) 0.76
d) 1.5

View Answer

c
Explanation:




6 - Question

Which instrument produces frequency domain information?
a) Oscilloscope
b) Spectrum analyzer
c) Frequency divider
d) Beam analyzer

View Answer

b
Explanation: The test instrument for producing a frequency-domain display is the spectrum analyzer. Like the oscilloscope, the spectrum analyzer uses a cathode-ray tube for display, but the horizontal sweep axis is calibrated in hertz and the vertical axis is calibrated in volts or power units or decibels.




7 - Question

What is the band width required to pass a signal with t0=75×10-9 without excessive distortions?
a) 14MHz
b) 53.7MHz
c) 13.33MHz
d) 11.56MHz

View Answer

c
Explanation:




8 - Question

A pulse train has a rise time of 6 ns. What is the minimum bandwidth to pass this pulse train faithfully?
a) 58.3MHz
b) 42.6MHz
c) 812MHz
d) 41.5MHz

View Answer

a
Explanation:




9 - Question

A circuit has a bandwidth of 200 kHz. What is the fastest rise time this circuit will pass?
a) 1.5μs
b) 2.3μs
c) 1.2μs
d) 1.75μs

View Answer

d
Explanation:




10 - Question

Fourier analysis helps us to determine how much bandwidth a particular signal occupies.
a) True
b) False

View Answer

a
Explanation: Fourier analysis allows us to determine not only the sine wave components in any complex signal but also how much bandwidth a particular signal occupies. Although a sine or cosine wave at a single frequency theoretically occupies no bandwidth, complex signals obviously take up more spectrum space.

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