Avionics - Fundamentals of Electronics Quiz(MCQ)
A)
Amplifier
B)
Differential
C)
Attenuator
D)
Multiplexer

Explanation : An amplifier is a component that increases the amplitude of the input signal. The increase in amplitude is measured as gain. Gain is the ratio of the voltage of the input signal vs output signal.

A)
14
B)
71
C)
14000
D)
71400

Explanation : Gain = output voltage/input voltage = 700/0.05 = 14000.

A)
4V
B)
10V
C)
400V
D)
400mV

Explanation : Gain = output signal voltage / input signal voltage
Output signal amplitude = 20 x 0.02 = 400mV.

A)
dB
B)
dBm
C)
DB
D)
dBc

Explanation : When the gain or attenuation of a circuit is expressed in decibels, implicit is a comparison between two values, the output and the input. An often used reference level in communication is 1 mW. When a decibel value is computed by comparing a power value to 1 mW, the result is a value called the dBm. It is computed with the standard power decibel formula with 1 mW as the denominator of the ratio.

A)
32
B)
54.4
C)
64
D)
64.4

Explanation : dB = 20 log(5/0.003) = 20 log 1666.67 = 20 x 3.22 =64.4.

A)
19
B)
20
C)
24
D)
240

Explanation : Total gain = product of individual gains = 6 x 8 x5 = 240.

A)
87.5mW
B)
87.5W
C)
13W
D)
13mW

Explanation : Gain = power out / power in
Power in = power out / gain = 7/80 = 87.5mW.

A)
Resistance offered to ac current by coil and capacitance
B)
Resistance offered to dc current by resistor
C)
Resistance offered to ac current by resistor only
D)
Resistance offered to dc current by coil and capacitance

Correct Answer :   Resistance offered to ac current by coil and capacitance

Explanation : Both coils and capacitors offer an opposition to alternating current flow known as reactance, which is expressed in ohms. Like resistance, reactance is an opposition that directly affects the amount of current in a circuit.

A)
Phase of voltage leads the current
B)
Phase of current leads the voltage
C)
Phase of current and voltage gets added
D)
Phase of current and voltage cancel out each other

Explanation : In addition to resistance of alternating current flow, a capacitor alters the phase difference between the current and voltage. The capacitor lowers the phase of the voltage and hence the current leads the voltage.

A)
Phase of current leads the voltage
B)
Phase of current and voltage gets added
C)
Phase of voltage leads the current
D)
Phase of current and voltage cancel out each other

Explanation : In addition to a resistance of alternating current flow, an inductor/coil alters the phase difference between the current and voltage. The inductor/coil lowers the phase of the current and hence the voltage leads the current.

A)
30KHz
B)
42.7KHz
C)
57.05MHz
D)
350KHz

Explanation : Bandwidth = resonant frequency / Quality factor = 28 x 106 /80 = 350KHz.

A)
250MHz
B)
512MHz
C)
533MHz
D)
720GHz

Explanation :

13 .
What is the Q factor for a 3-μH inductor with a total resistance of 45Ω at 90 MHz?
A)
37.68
B)
29.22Ω
C)
32.75Ω
D)
37.68Ω

Explaination : Quality factor = Q = 2πfL/R = (2 x 3.14 x 90 x 106 x 3 x 10-6)/45 = 1695.6 / 45 = 37.68.

A)
Increases
B)
Decreases
C)
Goes to infinite
D)
Remains constant

Explanation : Capacitative reactance is inversely proportional to the operating frequency and is given by the formula Xc= 1/2πfC where C is the capacitance value in Farad.

A)
2?
B)
200?
C)
700.16?
D)
796.2?

Explanation : Capacitative reactance =Xc= 1/2πfC = 1/(2 x 3.14 x 2 x 106 x 100 x 10-12) = 796.2Ω.

A)
Increases with less capacitance value
B)
Increases when lead wires a are lengthy
C)
Reduces when chip capacitors are used
D)
Reduces with decrease in size of lead wires

Correct Answer :   Increases with less capacitance value

Explanation : The lead wires of capacitors behave as a complex RLC circuit and generate stray capacitance. This can be reduced by shortening the length of the lead wires or using chip capacitors. However, decreasing or increasing the value of capacitance does not affect stray capacitance.

A)
Increases
B)
Decreases
C)
Goes to infinite
D)
Remains constant

Explanation : Inductive reactance is directly proportional to the operating frequency and is given by the formula Xf= 2πfL where L is the inductance value in Henry.

18 .
What is the inductive reactance of a 40-μH coil at 18 MHz?
A)
0
B)
4522H
C)
4000Ω
D)
4522Ω

Explaination : Inductive reactance = XL=2πfL = 2 x 3.14 x 18 x 106 x 40 x 10-6 = 4522Ω.

A)
Frequency damping circuit
B)
Frequency selective circuit
C)
Amplitude damping circuit
D)
Amplitude selective circuit

Correct Answer :   Frequency selective circuit

Explanation : A filter is a frequency-selective circuit. Filters are designed to pass some frequencies and reject others. Filters are used to reduce noise and increase selectivity.

A)
Differential filters
B)
Continuous filters
C)
Active filters
D)
Passive filters

Explanation : Simple filters created by using resistors and capacitors or inductors and capacitors are called passive filters because they use passive components that do not amplify. In communication work, many filters are of the passive LC variety, although many other types are used.

A)
Low pass filters
B)
High pass filters
C)
Band pass filters
D)
All pass filters

Correct Answer :   All pass filters

Explanation : An all pass filter passes all frequencies equally well over its design range but has a fixed or predictable phase shift characteristic. Filters normally attenuate the signal applied for some values of frequency whereas an all pass filter retains the signal level at all frequencies.

A)
Low pass filter
B)
High pass filter
C)
Band pass filter
D)
All pass filter

Correct Answer :   High pass filter

Explanation : An RC coupling circuit is an example of a high-pass filter because the AC component of the input voltage is developed across R and the DC voltage is blocked by the series capacitor. Furthermore, with higher frequencies in the AC component, more AC voltage is coupled.

A)
Ripple
B)
Roll in
C)
Roll off
D)
Envelope delay

Explanation : Roll off is also called the attenuation rate, roll-off is the rate of change of amplitude with frequency in a filter. The faster the roll-off, or the higher the attenuation rate, the more selective the filter is, i.e., the better able it is to differentiate between two closely spaced signals, one desired and the other not.

A)
Insertion loss
B)
Attenuation
C)
D)
passband loss

Explanation : Insertion loss is the loss the filter introduces to the signals in the passband. Passive filters introduce attenuation because of the resistive losses in the components. Insertion loss is typically given in decibels.

25 .
What is the value of resistor for a high pass RC filter to produce a cutoff frequency of3.4KHz if C = 0.047μF?
A)
654Ω
B)
752Ω
C)
996Ω
D)
1000Ω

Explaination :

26 .
What is the type of filter shown in the figure?
A)
Band pass filter
B)
High pass filter
C)
Low pass filter
D)
All pass filter

Correct Answer :   Low pass filter

Explaination : The simplest form of low-pass filter is the RC circuit shown in the figure. The circuit forms a simple voltage divider with one frequency-sensitive component, in this case, the capacitor. At very low frequencies, the capacitor has very high reactance compared to the resistance and therefore the attenuation is minimum. Thus allowing lower frequencies to pass through while attenuating higher frequency signals.

A)
Digital pulses
B)
Harmonic
C)
Square wave
D)
Complex wave

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.

A)
25%
B)
50%
C)
100%
D)
200%

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%.

29 .
What is the frequency of 7th harmonic of a 2KHz sine wave?
A)
2KHz
B)
5KHz
C)
9KHz
D)
14Khz

Explaination : The frequency of 7th harmonic sine wave = 7 x 2KHz = 14KHz.

A)
True
B)
False
C)
Can Not Say
D)
None of the above

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.

A)
1.2?s
B)
1.5?s
C)
1.75?s
D)
2.3?s

A)
41.5MHz
B)
42.6MHz
C)
58.3MHz
D)
812MHz

Explanation :

A)
Oscilloscope
B)
Beam analyzer
C)
Frequency divider
D)
Spectrum analyzer

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.

A)
0.52
B)
0.74
C)
0.76
D)
1.5