exam for Electronic Engineering

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EE-1301: Modern Electronic Technology Spring 2018 Exam #2 Study Guide

Test Scheduled for Friday, April 6, 2018 Overall:

 The test is open-book, open-notes, and closed-friends.  A laptop computer is allowed for access to class notes, handouts, homework, labs, etc.  Bring a writing instrument and a calculating instrument

Test room and seating:  147 Caruth Hall  Section 001 (11:00-11:50): Please sit in pairs with an empty seat between pairs of students.  Section 002 (12:00-12:50): Please leave an empty seat between you and your neighbor.

You are responsible only for material that we have covered in the course pack and related handouts, materials, labs, notes, etc. The focus will be on material since the last test, although you are always responsible for Kirchhoff’s Voltage and Current Laws, Ohm’s Law and the Power Law.

Course Pack: (pages 75-91, 95-103, 109-139)

Electronic switching: a historical perspective of the relay, the vacuum tube, the transistor and the integrated circuit; current flow and electron flow in the vacuum tube, P-N junction diode, bipolar junction transistor, field-effect transistors, binary counting.

Relay operation: A relay is either on or off, but not partially on or off. The relay can only turn on and off a few hundred times per second. On the other hand, transistors and vacuum tubes can be on, off, or partially on or off. The current can be smoothly varied from maximum to minimum, and it can turn on and off millions or billions of times per second.

Vacuum tube and transistor operation: In the vacuum tube, a negative voltage applied to the grid reduces (ultimately cutting off) the emission of electrons from the filament; hence the plate current can be smoothly varied from a maximum value to zero. In a bipolar junction transistor, the base- emitter voltage controls the collector current. In field effect transistors, the gate-source voltage controls the drain current. In relays, vacuum tubes, and transistors, a small amount of power at the input can control a large amount of power at the output. Silicon Run video.

Integrated circuit operation: An integrated circuit (IC), sometimes called a chip or microchip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated. An IC can function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor. For application in computers, ICs are configured in specific switching functions called gates: NOT, AND, NAND, OR, NOR, OR, XOR. Truth tables describe the input-output relationship of these gate functions.

Clocks: a historical perspective of the clock – sundial, water clock, weight clock, sand clock, candle clock, pendulum clock, quartz clock, atomic clock; property for measurement of passage of time; integration of digital logic.

Exponential decay and measuring time constants.

Sound waves and sine waves: amplitude, rms amplitude, peak-to-peak amplitude, period, and frequency. Given a sine wave display, find the amplitude and period, and calculate the frequency? Given amplitude and frequency, determine the period and sketch a sine wave?

Laboratories: Lab 4 (The Relay); Lab 5 (Charge Storage in Capacitors); Lab 7 (Ring Oscillator); Lab 8 (Transistor Amplifier)

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EXAMPLE QUESTIONS

1. Under normal conditions a diode does not conducts current when it is

A. reverse‐biased. B. forward‐biased. C. avalanched. D. saturated.

2. The movement of holes in a conductor is called

A. voltage. B. current. C. recombination. D. equilibrium.

3. Which statement best describes a semiconductor?

A. A material with many free electrons. B. A material with very few free electrons. C. A material with few free electrons. D. No description fits.

4. Silicon uses four electrons to form bonds with adjacent silicon atoms. If silicon atoms are replaced with atoms with three electrons for bonding, this produces:

A. a pn junction. B. a p‐type material. C. a n‐type material. D. faster electrons.

5. An ideal diode presents a(n) __________when forward-biased and a(n) _________when reverse- biased.

A. open, short B. short, open C. open, open D. short, short

6. A forward-biased diode has the __________ connected to the positive side of the source, and the _________ connected to the negative side of the source.

A. cathode, anode B. cathode, base C. base, anode D. anode, cathode

7. A P-N junction mimics a closed switch when it:

A. forward biased. B. is reverse biased. C. cannot overcome its barrier voltage. D. has a wide depletion region.

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8. A transistor may be used as a variable resistor or as a:

A. fixed resistor B. tuning device C. rectifier D. switching device

9. For the circuit at the right, the switch is closed to charge the capacitor to 9V and then opened to discharge the capacitor through the resistor R. If the time constant (tau) is 10 seconds for the exponential decay, determine the voltage difference across the capacitor at 10 seconds.

At one time constant, the voltage has dropped to 37% of the initial value = 0.37x9V = 3.33 V

10. A 22 microfarad capacitor is charged until it stores 0.002 C. Calculate the voltage across the capacitor.

0.002 22 10

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11. The base-2 representation for the base-10 number 12 is:

A. 001111 B. 010111 C. 001100 D. 101010

12. The output of an AND gate with three inputs, X, Y, and Z, is HIGH when _____

A. X = 0, Y = 0, Z = 0 B. X = 0, Y = 0, Z = 1 C. X = 1, Y = 1, Z = 1 D. X = 1, Y = 0, Z = 0

13. The output of a NOR gate is LOW if _____

A. all inputs are HIGH B. any input is HIGH C. any input is LOW D. all inputs are LOW

14. The format used to present the logic output for various combinations of logic inputs is called a(n) ______

A. Boolean constant B. Boolean variable C. truth table D. input logic table

C9 V

R = 50K 

R

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15. Warren Marrison used this knowledge to create a clock that kept time by counting the vibrations of a mineral crystal. What was the mineral that in 1969 was also used to regulate the time the world's first electronic wristwatch?

A. Pendulite B. Cesium crystal

C. Quartz D. Regulite

16. Which chemical element has a resonant state that is used in the atomic clock that is used to define the standard second?

A. Hydrogen

B. Cesium C. Rubidium D. Mercury

17. Why does the shadow on a sun dial move in a “counter clockwise” direction in the Southern Hemisphere?

A. Because the gears the gears turn that direction. B. Because electrons are right-handed. C. Because Galileo made his first clock to turn that way. D. Shadow on a sundial rotates that way.

18. If a 3-input NOR gate has eight b i n a r y input possibilities, how many of those possibilities will result in a HIGH output?

A. 1 B. 2 C. 3 D. 4

19. Quartz clocks watches use a quartz crystal that resonates at 32,768 Hz because

A. all quartz crystals resonate at that frequency.

B. a 15-bit binary counter outputs a HIGH when it counts 215 pulses. C. all quartz crystals resonate most efficiently at that frequency. D. this frequency is mandated by an international agreement that sets standards for

quartz clock and watch operation.

20. If a signal passing through a gate is inhibited by sending a LOW into one of the inputs, and the output is HIGH, the gate is a(n):

A. AND B. NOR C. OR D. NAND

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21. Complete the Truth Table for the circuit below

X

A

B

C

A B C ̅ ̅

0 0 0 0 0 1

0 0 1 0 1 0

0 1 0 1 1 0

0 1 1 1 1 0

1 0 0 0 0 1

1 0 1 0 1 0

1 1 0 0 0 1

1 1 1 0 1 0

22. A sound wave with pressure amplitude of 0.02 N/m2 has a sound loudness level of 60

dB. If the pressure amplitude increases to 0.63 N/m2, the new sound loudness level is approximately ___________?

A. 63.2 dB B. 123.3 dB C. 90 dB 60 dB + 20log(0.63/0.02) D. 75 dB

23. Most of the electrons in the base of an NPN transistor flow:

A. out of the base lead. B. into the collector. C. into the emitter. D. into the base supply.

24. In a transistor, collector current is controlled by:

A. collector current. B. base current. C. collector resistance. D. all of the above.

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25. The graph below shows the exponential decay of the voltage difference across a capacitor. Determine the time constant.

TC  0.75 sec

26. With the positive probe on the base of an NPN transistor, an ohmmeter reading between the other transistor terminals should be:

A. open. B. infinite. C. low resistance. D. high resistamce.

27. In a “n” type material, majority carriers would be:

A. holes. B. dopants. C. slower. D. electrons

28. When is a PN junction formed?

A. in a depletion region. B. in a large reverse-biased region. C. the point at which two oppositely doped materials come together. D. whenever there is a forward voltage drop.

29. Doping of a semiconductor material means

A. that a glue-type substance is added to hold the material together. B. that impurities are added to increase the resistance of the material. C. that impurities are added to decrease the resistance of the material. D. that all impurities are removed to get pure silicon.

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30. Subtract 910 from 1710 in binary:

1 0 0 0 1

1 0 0 1

31. A wave has a period of 45 ms. Its frequency is ________.

A. 6.66 Hz B. 44.44 Hz C. 22.22 kHz D. 22.22 Hz = 1/0.045 sec

32. The frequency of a pulse train is 4 kHz. The pulse period is ________.

A. 5 ms B. 250 ms C. 400 s D. 250 µs

33. What is the amplitude of this signal? A. 1 cm B. 2 cm C. 4 cm D. 3.1 cm E. 1.55 cm

34. Given a baseline pressure of 2.94 X 10-9 psi, how many dB will a pressure wave of 9.2345 X 10-6 psi measure?

A. 69.9 dB = 20log(9.2345 x 10-6/2.94 x 10-9) = 20log(3141) B. 51.4 dB C. 34.9 dB D. 84.1 dB

35. A jet taking off 200 feet away measures 110 dB. Dallas Fort-Worth airport has 7 runways, 4 of which that can operate at the same time. If you stand between 2 operational runways, 200 feet away from each, and two jets takeoff together, how loud of a sound would be measure?

Find the 2’s complement of 01001 then add to 10001: 10110 + 1 1 0111

1 0 0 0 1

1 0 1 1 1

1 0 1 0 0 0 The left-most 1 means the answer is + so the answer is +01000; this is decimal 8.

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Since these signals look like noise, we add the powers then calculate 10log(sum). 110 dB corresponds to 0.1 W/m2. The intensity for two 110 dB jet engine sounds is 0.2 W/m2. The intensity for the sum is: I(dB) = 10log(0.2/10-12) = 113 dB

36. A Fourier series describes

A. The combinations of fundamental tones and overtones that give musical instruments their characteristic sounds.

B. The amplitudes and frequencies of signals that comprise voice and music. C. Only the frequencies of tones present in voice and musical sounds. D. (A) & (B).

37. When sound travels through air, the air particles ______.

A. vibrate along the direction of wave propagation B. vibrate but not in any fixed direction C. vibrate perpendicular to the direction of wave propagation D. do not vibrate

38. When a wave travels through a medium ______.

A. particles are transferred from one place to another B. energy is transferred in a periodic manner C. energy is transferred at a constant speed D. none of the above statements is applicable

39. The frequency of a wave travelling at a speed of 500 ms-1 is 25 Hz. Its time period will be

______.

A. 20 s B. 0.05 s C. 25 s D. 0.04 s

40. The amplitude of a wave is ______.

A. the distance the wave moves in one second B. the distance the wave moves in one time period of the wave C. the maximum distance moved by the medium particles on either side of the mean

position D. the distance equal to one wave length

41. Sound waves do not travel through

A. Solids B. Liquids C. Gases D. Vacuum

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42. The physical quantity, which oscillates in most waves, is

A. mass B. energy C. Instantaneous displacement D. wavelength

43. Sound waves are

A. longitudinal B. transverse C. partly longitudinal and partly transverse D. sometimes longitudinal and sometimes transverse

44. The frequency which is not audible to the human ear is ___________

A. 50 Hz B. 500 Hz C. 5000 Hz D. 50,000 Hz

45. The speed of sound in medium depends upon _______

A. Amplitude B. Frequency C. Wavelength D. properties of the medium

46. A sound source sends waves of 400 Hz. It produces waves of wavelength 2.5 m. The velocity of sound waves is

A. 100 m/s B. 1000 m/s C. 10,000 m/s D. 3000 km/s

47. The time period of a vibrating body is 0.05 s. The frequency of waves it emits is ______.

A. 5 Hz B. 20 Hz C. 200 Hz D. 2 Hz

48. A condenser microphone changes sound into an electrical signal using

A. A metallic film moving in a magnetic field. B. Capacitive effects of a moving plate. C. A moving coil inside a magnetic field. D. A quartz crystal that changes pressure into voltage.

49. A ribbon microphone changes sound into an electrical signal using

A. A metallic film moving in a magnetic field. B. Capacitive effects of a moving plate. C. A moving coil inside a magnetic field. D. A quartz crystal that changes pressure into voltage.