ASSIGNMENT 1

ASSIGNMENT 1Textbook assignment: Chapter 1, “Introduction to Electron Tubes,” pages 1-1 through 1-56._________________________________________________________________________________1-1. The electrons emitted by a heatedconductor come from what source?1. An external battery2. An external ac source3. Both 1 and 2 above4. The conductor itself1-2. What is another name for thermionicemission?1. The gap effect2. The heat effect3. The Edison effect4. The Fleming effect1-3. Electrons emitted by a hot filament areable to cross the gap between thefilament and the plate. What forceenables them to do this?1. Magnetic repulsion2. Inductive reactance3. Thermionic emission4. Electrostatic attraction1-4. Name the two series circuits that areassociated with a diode electron tube.1. The plate and anode circuits2. The plate and filament circuits3. The battery and filament circuits4. The filament and cathode circuits1-5. When an ac voltage is applied across theplate and filament of a diode, the currentmeasured will represent what type ofwaveform?1-6. A filament that uses a one-moleculethicklayer of barium and strontium isclassified as what type of filament?1. Tungsten2. Oxide-coated3. Tungsten-strontium4. Thoriated-tungsten1-7. Which of the following ac filamentvoltages is most likely to be considereda common voltage?1. 1.5 volts2. 3.0 volts3. 6.3 volts4. 9.0 volts1-8. An ac directly heated filament haswhich of the following advantages?1. Even spacing relative to the plate2. Even emission across the filament3. Constant emission throughout the accycle4. Rapid heating effect1-9. An indirectly heated cathode alwaysuses what material for its emittingsurface?1. An oxide coating2. A thorium coating3. A tungsten coating4. A graphite coating1. Pulsating dc2. Dc3. Pulsating ac4. Ac1

1-10. What is the principal advantage of anindirectly heated cathode over a directlyheated cathode?1. It is larger2. It is immune to ac heater currentvariations3. It reaches an operating temperaturemore quickly4. It has a lower operating temperature1-11. When you view an electron tube and itssocket connection from the bottom, inwhat direction are (a) the pins of thetube and (b) the pins of the socketnumbered?1. (a) Counterclockwise(b) Clockwise2. (a) Counterclockwise(b) Counterclockwise3. (a) Clockwise(b) Counterclockwise4. (a) Clockwise(b) Clockwise_______________________________________IN ANSWERING QUESTIONS 1-14THROUGH 1-16, MATCH EACH TERMLISTED IN COLUMN A WITH ITSASSOCIATED ELECTRONIC SYMBOLLISTED IN COLUMN B.A. TERMS B. SYMBOLS1-14. Dc plate resistance 1. E p1-15. Dc plate current 2. e p1-16. Dc plate voltage 3. I p4. R p_______________________________________1-12. Electron tubes are identified by anumber preceded by which of thefollowing letter designations?1. T2. V3. ET4. VT1-13. The getter in an electron tube serveswhat purpose?1. It protects the plate fromoverheating2. It allows the cathode to emit moreelectrons3. It helps to produce a better vacuum4. It anchors the tube elements in thebaseFigure 1A. — E p — I p characteristic curve.IN ANSWERING QUESTIONS 1-17THROUGH 1-23, REFER TO FIGURE 1A.1-17. The area of the graph that lies betweenpoints C and D is referred to as1. nonlinear2. straight3. linear4. curved2

1-18. In most applications, a designer wouldtry to ensure that an electron tubeoperates at which of the followingpoints on the curve?1. A2. B3. C4. D1-19. An electron tube operating at point A onthe curve would have what plateresistance?1. 7 k W2. 10 k W3. 30 k W4. 100 k W1-20. An electron tube operating at point Dcan be said to be in what condition?1. Plate saturation2. Cathode saturation3. Both 1 and 2 above4. Normal operation_______________________________________MATCH EACH ELECTRON- TUBEOPERATING CHARACTERISTIC INCOLUMN A WITH ITS CORRESPONDINGCHARACTERISTIC- CURVE POINT INCOLUMN B.A. CHARACTERISTICS B. POINTS1-21. Conduction occurs only atthe outer fringe of thespace charge1-22. All the electrons of thespace charge are attractedto the plate1-23. The point at which the tubecan be operated mostefficiently1. A2. B3. C4. D1-24. An electron tube is operated at 300 voltsand a plate current of 60 milliamperes.To avoid being damaged, the tube musthave what minimum plate dissipationrating?1. 5000 watts2. 18 watts3. 5 watts4. 0.18 watt1-25. Under which of the following conditionscan a tube be considered operatingbeyond its peak inverse voltage rating?1. When the plates glow cherry red2. When current flows from the plateto the cathode3. When current flows from thecathode in the form of an arc4. When current flows from thecathode to the plate and damageoccurs1-26. Why does control grid voltage of atriode exercise greater control than platevoltage over conduction of the tube?1. The grid is operated at a highervoltage than the plate2. The grid adds electrons to theelectron stream3. The grid is closer to the plate thanthe cathode4. The grid is closer to the cathodethan the plate1-27. The plate load resistor in an electrontubecircuit performs what function?1. It converts variations in platevoltage to current variations2. It limits the amount of plate voltagethat can be applied to the tube3. It converts variations in platecurrent to variations in plate voltage4. It limits the amount of plate currentthat can flow through the tube_______________________________________3

1-31. A triode electron tube is designed toconduct at 15 milliamperes of currentwhen its grid is at 0 volts relative to itscathode. For every volt below this,conduction will decrease by 1.5milliamperes. If the tube is biased at -3volts and has a 6-volt peak-to-peak inputsignal, what is the minimum amount ofcurrent that will conduct through thetube?Figure 1B.—Triode operation.1-28. The triode circuit depicted in figure 1Babove contains a 50 k W load resistor.When a 10-volt peak-to-peak ac signalis applied to the grid, current flow in thetube varies between 5 milliamperes and12 milliamperes. What is the peak-topeakamplitude of the output?1. 500 volts2. 350 volts3. 250 volts4. 150 volts1-29. Most amplifier circuits are designed tooperate with the grid negative in relationto the cathode. This is done to avoidwhich of the following problems?1. 11.5 milliamperes2. 6.0 milliamperes3. 1.5 milliamperes4. 0 milliamperes1-32. Overdriving can be considered a form ofdistortion for which of the followingreasons?1. The output is not in phase with theinput2. The output does not have the samepolarity as the input3. The output is not a faithfulreproduction of the input4. The output does not have the sameamplitude as the inputTHIS SPACE LEFT BLANKINTENTIONALLY.1. Excessive grid current2. Excessive plate current3. Distortion on small signals4. Distortion on large negative signals1-30. A triode amplifier has 350 volts appliedto its plate across a 25 k W load resistor.With no input signal applied and a biasvoltage of -9 volts, 4 milliamperesconducts across the tube. What is thequiescent plate voltage?1. 0 V2. 100 V3. 250 V4. 350 V4

_______________________________________IN ANSWERING QUESTIONS 1-33THROUGH 1-35, MATCH EACHCONDITION AFFECTING TRIODEAMPLIFIER OPERATION IN COLUMN AWITH ITS CORRESPONDING ELECTRONICTERM IN COLUMN B.A. CONDITIONS B. TERMS1-33. Condition that existswhen the positive andnegative excursions ofthe output are"flattopped"1-34. A form of distortionthat can occur onlyduring the positiveexcursion of the acinput of a triodeamplifier1-35. A form of distortionthat can only occur in atriode amplifier duringthe negative excursionof the input1.2.3.4.CutoffSaturationOverdrivingCurrentlimiting_______________________________________1-36. Electronic equipment that uses fixedbias for its tube circuit receives its gridbiasvoltage from what source?1. A portion of the plate voltage2. A power source internal to thecircuit3. Both 1 and 2 above4. A power source external to thecircuit1-37. The effect of both cathode and gridbiasing is to make the cathode (a) whatpolarity, relative to (b) what other tubeelement?1. (a) Positive (b) the plate2. (a) Negative (b) the plate3. (a) Positive (b) the grid4. (a) Negative (b) the grid1-38. Which of the following types of biasingis most likely to use a battery supply?1. Self2. Grid3. Fixed4. Cathode1-39. In an electron tube circuit using cathodebiasing, the cathode is made positive inrelation to the grid. This is done by avoltage dropped across what circuitelement?1. R L2. R k3. C c4. C k1-40. The cathode bias voltage level appliedto the cathode is maintained at aconstant level by what circuitcomponent?1. R L2. R k3. C c4. C k5

1-41. Which of the following undesirablecharacteristics is associated withcathode biasing?1. Plate voltage is increased by thevoltage amount of biasing2. The cathode is forced to operate at apositive potential3. The maximum negative output islimited4. Current must flow in the circuitcontinuously1-42. Grid-leak biasing develops a biasingvoltage from (a) what portion of theinput signal and (b) by what type ofaction?1. (a) Negative (b) resistive2. (a) Negative (b) capacitive3. (a) Positive (b) capacitive4. (a) Positive (b) resistive1-43. During the charge cycle in grid-leakbiasing, C c , draws current through whatcircuit element?1. R g2. rgk3. R L4. R k1-44. During the discharge cycle in grid-leakbiasing, C c discharges across whatcircuit element?1. R g2. rgk3. R L4. R k1-45. The effect of grid-leak biasing is torectify the input signal. Because of this,the amplitude of the biasing voltagedepends upon which of the followingfactors?1. Amplitude of the input2. Frequency of the input3. Size of R g and C c4. All of the above1-46. During the charging cycle in grid-leakbiasing, the effective size of rgk isdecreased. This is caused by whatelectronic principle?1. Electrostatic repulsion between thegrid and the plate2. Electrostatic repulsion between thegrid and the cathode3. Electrostatic attraction between thecathode and the grid4. Electrostatic attraction between theplate and the cathode1-47. The charge and discharge of capacitorC c , used in grid-leak circuits, will beequal when what condition occurs?1. When Rgk becomes the same valueas Rg2. When C c reaches its maximumcharge-holding capacity3. When the charge on C c cuts the tubeoff4. When R g becomes larger than rgk_______________________________________IN ANSWERING QUESTIONS 1-48THROUGH 1-50, MATCH EACHCHARACTERISTIC OF AMPLIFIEROPERATION IN COLUMN A WITH ITSASSOCIATED CLASS OF AMPLIFIER INCOLUMN B.A. CHARACTERISTICS B. CLASSES1-48. Conduction occurs in thetube during only 50% ofthe entire input cycle1-49. Conduction occurs in thetube throughout the entireinput cycle1-50. Conduction occurs in thetube for more than 50%,but less than 100% of theentire input cycle1.2.3.4.AABBC_______________________________________6

1-51. A triode amplifier has a load resistorrated at 150 k W. A +3-volt signal willcause 4 milliamperes of current toconduct through the tube. What is thevoltage gain of the amplifier?1. 4502. 2003. 1004. 501-52. The amplification factor for an electrontube is identified by what electronicsymbol?1. A r2. V g3. g m4. m1-53. The grid voltage on an electron tube isincreased from 2 volts to 4 volts. Thiscauses plate current to increase from 2milliamperes to 5.5 milliamperes. Thissame increase in plate current can beachieved by keeping the grid at +2 voltsand raising the plate voltage from 200volts to 400 volts. What is the mu of thetube?1. 4002. 2003. 1004. 501-54. What is the transconductance for thetube described in question 1-53?1. 175 mmhos2. 645 mmhos3. 700 mmhos4. 1750 mmhos1-56. In a triode, what interelectrodecapacitance has the greatest effect ontube operation?1. C pg2. C gk3. C pk4. C sg1-57. Interelectrode capacitance (C pg ) affectsthe gain of a triode stage because ofwhat electronic feature?1. Blocking2. Feedback3. Transit time4. Phase inversion1-58. The action of the screen grid in reducinginterelectrode capacitance can beexpressed mathematically as1.2.3.4.1-59. For normal operation, the screen grid ofa tetrode is operated at a positive voltagein relation to (a) what tube element, andnegative in relation to (b) what othertube element?1. (a) Grid (b) plate2. (a) Grid (b) cathode3. (a) Plate (b) grid4. (a) Cathod (b) grid1-55. Transconductance is identified by whatelectronic symbol?1. m2. g m3. rgk4. t c7

1-63. The suppressor grid of a pentode isoperated at what potential relative to(a) the cathode and (b) the plate?Figure 1C.—Basic tetrode circuit.1-60. What is the function of C sg in figure 1Cabove?1. It serves as a feedback capacitor2. It bypasses ac signals from thescreen grid to ground3. It keeps dc voltages from beingapplied to the screen grid fromground4. It couples ac signals from thecathode to the screen grid1-61. Which of the following undesirablecharacteristics is/are associated withtetrode operation?1. The plate is isolated from theelectron stream2. The plate emits secondary emissionelectrons3. The output is noisy4. Both 2 and 3 above1-62. Generally, tetrodes have a lowertransconductance than triodes. This iscaused by what feature of a tetrode?1. The plate is isolated from theelectron stream2. The screen grid draws current fromthe electron steam3. Secondary emission limits theamount of current the plate can drawfrom the electron stream4. The screen grid is operated at anegative potential relative to theplate and electrons are repelled fromthe plate1. (a) Positive(b) The same potential2. (a) Negative(b) The same potential3. (a) The same potentia(b) Negative4. (a) The same potential(b) Positive1-64. Voltage is supplied to the suppressorgrid in a pentode from what source?1. Through a resistor from the platesource voltage2. Through a resistor from ground3. By a separate voltage source4. By a physical connection from thecathode1-65. The suppressor grid is able to control theeffects of secondary emission by usingwhich of the following electronicactions?1. By attracting electrons emitted bythe plate through electromagneticattraction2. By repelling electrons emitted bythe plate through electromagneticrepulsion3. By attracting electrons emitted fromthe plate through electrostaticattraction4. By repelling electrons emitted fromthe plate through electrostaticrepulsion8