Description : When a solid-state component of an electronic circuit is mounted to a metallic mass, the general purpose of that mass is to ____________. A. prevent vibration damage to delicate components B. prevent ... damage to solid-state components C. dissipate stray magnetic currents D. act as a heat sink
Last Answer : Answer: D
Description : Which of the following actions can be carried out in order to prevent thermal runaway in a transistor? A. Increase the current through the collector-base junction. B. Install a heat sink. ... point to increase collector current. D. Increase the potential difference between the emitter and the base.
Last Answer : Answer: B
Description : Which of the following statements is true about the illustrated circuit? EL-0030 A. The field rheostat is used for manual voltage control. B. if the generator is flat compounded then the field rheostat ... to act like a series motor and overspeed with the controller in the full raise position.
Last Answer : Answer: A
Description : Heat sinks are frequently used with _____________. A. power transistors B. vacuum tubes C. tunnel rectifier diodes D. all of the above
Description : A reverse-current relay will prevent AC generator motorization by ____________. A. automatically redirecting the load B. automatically speeding up the prime mover C. tripping the panel board main switch D. tripping the generator circuit breaker
Description : When using an ohmmeter to test a semiconductor diode, you find a low resistance in both the forward and reverse bias directions. This indicates that the diode has a/an ____________. A. open B. short C. good resistive quality D. good capacitive quality
Description : The device in figure 'B' shown in the illustration will conduct when the ____________. EL-0067 A. base-emitter is forward biased and the collector-base is reverse biased B. anode-cathode is forward ... is reversed biased D. terminal 1-2 is forward biased and the emitter-terminal 1 is reverse biased
Description : Tunnel diode is a: a) Power diode b) Has light doping c) Has heavy doping d) Is a reverse recovery diode Ans: C 76.LEDs are fabricated from: a) Silicon b) Germanium c) Si or Ge d) Gallium arsenide
Last Answer : Ans: D
Description : An important characteristic of the device shown in figure 'B' of the illustration as compared with conventional NPN or PNP transistors is its ____________. EL-0065 A. higher temperature sensitivity B. higher power ratings C. very high input resistance D. all of the above
Last Answer : Answer: C
Description : Power transistors with heat sink are fixed by
Last Answer : Power transistors with heat sink are fixed by Fastening
Description : As shown in the illustration, a 'pitch cutback' feature is incorporated in the system. This circuit reduces pitch amount to prevent engine overload when it senses ____________. EL-0095 A. pitch error of ... servo' C. excessive propeller speed or fuel to either engine D. only one engine on the line
Description : In the illustration, the diode between terminals 16 and 17 is to _________. EL-0046 A. insure that the voltage across the governor coil (EG-3P) never exceeds .6 VDC B. compensate for the ... heating up C. protect the electronic governor from counter EMF D. act as a filter to prevent hunting
Description : When replacing a power transistor fitted with a heat sink in a circuit, a coating of silicone grease is applied between the transistor case and the heat sink. This is done to ____________. A. lubricate ... the heat sink C. aid in the removal of the heat sink D. provide maximum heat transfer
Description : One of the generator or motor bearings is generally insulated from the end housing in order to prevent ________. A. rapid brush wear B. current leakage from the shaft C. excessive field winding heat D. circulation of shaft currents induced in the machine's frame
Description : You are testing the insulation in an AC generator with a megohmeter. The resistance value of a dry, clean winding will ____________. A. continue to rise as the test potential is maintained, ... fairly steady after 5 to 7 minutes D. stabilize after approximately 2 to 4 minutes of fluctuation
Description : A solid-state circuit is inoperative; the FIRST action that should be taken is to ____________. A. wiggle all the components to check for loose connections B. check all the resistors C. change all transistors D. check the DC supply voltage
Description : A transformer in an electric circuit serves to ____________. A. generate its own electrical power B. transform electrical energy into mechanical energy C. increase or decrease circuit voltage as required D. convert AC current to DC current
Description : Increasing the load to the secondary windings of a transformer will cause a/an ____________. A. decrease in the primary voltage B. increase in the primary voltage C. decrease in the primary current D. increase in the primary current
Description : Electric cables are formed of stranded wire to ____________. A. increase the current carrying capability for a given size wire B. increase their flexibility C. decrease the weight for a given size wire D. assure good conductivity at junction points
Description : A loud buzzing noise coming from the contacts in a magnetic controller can be caused by ____________. A. excessive current B. excessive magnet gap C. bouncing of contacts D. dirt on magnet faces
Description : If the contacts of a motor starter or controller fail to drop out when the 'stop' button is depressed the ____________. A. contacts are carrying excessive current B. contacts have become welded together C. shading coil is broken D. shading coil is loose
Description : One of the generator bearing shells is generally insulated from the end housing in order to prevent _____________. A. rapid brush wear B. residual magnetism leak off C. excessive field winding heat D. circulation of shaft currents
Description : Refering to the illustrated schematic diagram, which of the following statements is true when the motor is running in the forward direction? EL-0011 A. Normally-open contacts '4-5' are closed. B. Current ... switch. C. Normally-closed contacts 'R' are open. D. The blowout coils must be closed.
Description : The purpose of a main switchboard circuit breaker's reverse-power trip is to _____________. A. prevent main circuit overload B. protect the circuit breaker blowout coil C. prevent alternator motorization D. prevent low voltage tripout
Description : When charging lead-acid batteries, you should reduce the charging rate as the battery nears its full charge capacity to ______________. A. prevent excessive gassing and overheating B. allow equalization of cell voltages C. reduce lead sulfate deposits D. increase lead peroxide formation
Description : Junction breakdown occurs: a) With forward bias b) With reverse bias c) Under high temperature condition d) Because of excess heating of the diode
Last Answer : Ans: B
Description : The width of depletion layer of a P-N junction – (1) decreases with light doping (2) increases with heavy doping (3) is independent of applied voltage (4) is increased under reverse bias
Last Answer : (4) is increased under reverse bias Explanation: The total width of the depletion region is a function of applied reverse-bias and impurity concentration. Forward bias decreases the depletion region width whilst reverse bias increases it.
Description : The width of depletion layer of a P-N junction (1) decreases with light doping (2) increases with heavy doping (3) is independent of applied voltage (4) is increased under reverse bias
Last Answer : is increased under reverse bias
Description : Essential amino acids have been advocated as standard therapy for renal failure. Which of the following statements are true? A. Increased survival from acute renal failure has been reported ... BUN and creatinine to the same degree as solutions containing excessive nonessential amino acids.
Last Answer : Answer: BC DISCUSSION: Essential amino acids and hypertonic dextrose, as opposed to hypertonic dextrose alone, was reported by Abel and co-workers to be associated with a decreased mortality rate ... renal failure have not been carried out in sufficient numbers to yield answers to this question
Description : When you are making a high potential test on a piece of repaired electrical machinery, a rise in leakage current indicates ____________. A. good insulation B. bad insulation C. high insulation power factor D. a high slot discharge factor
Description : Reversing any two of the three rotor leads on a wound-rotor induction motor will _____________. A. increase motor performance B. decrease motor performance C. reverse the motor rotation D. have no effect on the direction of rotation or motor performance
Description : A capacitor discolored due to excessive heat should be _____________. A. calibrated using a capactance wheatstone bridge B. replaced and the reason for the overheating found C. cooled with a spray ... purpose D. resoldered with care taken to insure that the origional cold solder joint is repaired
Description : When choosing a battery for a particular application, major consideration should be given to the battery's ____________. A. amp-hour capacity B. terminal polarity C. stability under charge D. ambient temperature rise
Description : To increase the frequency of an operating AC generator, you should ____________. A. increase the field excitation B. decrease the field excitation C. increase the number of magnetic poles D. increase the speed of the prime mover
Description : The phase lead compensation is used to a) Increase rise time and decrease overshoot b) Decrease both rise time and overshoot c) Increase both rise time and overshoot d) Decrease rise time and increase overshoot
Last Answer : Ans: Decrease rise time and increase overshoot
Description : The outlet temperature of cooling water in a heat exchanger is generally not allowed to exceed above 50°C in industrial practice mainly to avoid (A) Its evaporation loss (B) Excessive corrosion (C) Uneconomic LMTD (D) Decrease in heat exchanger efficiency
Last Answer : (B) Excessive corrosion
Description : When charging lead-acid batteries, the charging rate should be reduced as the battery nears its full charge to ____________. A. prevent damaging battery plates B. allow equalization of cell voltages C. reduce lead sulfate deposits D. increase lead peroxide formation
Description : Current limited power supplies can prevent damage to A) Rectifier diodes and power transformers. B) Pass transistors C) Other circuits in the system D) All of the above.
Last Answer : D) All of the above.
Description : The function of the commutator in a DC motor is to ________. A. reverse the flow of current through the armature B. reverse the flow of current in the field poles C. reduce the reluctance of the magnetic path through the motor D. shift the neutral running plane of the brushes to prevent sparking
Description : The armature cores of the D.C. motors are constructed with laminations to ___________. A. eliminate hysteresis B. minimize brush sparking C. reduce eddy current losses D. compensate for armature reaction
Description : Voltage failure of an AC generator may be caused by ____________. A. failure of the exciter generator B. a tripped bus circuit breaker C. high mica segments on the stator bus bar D. excessive prime mover speed
Description : The air gap in an induction motor should be checked periodically with a feeler gage to detect ____________. A. rotor contact with the laminations B. changes in armature magnetic strength C. excessive bearing wear D. electrical damage to the rotor
Description : Violent gassing developed by a lead-acid battery during charging indicates that the ____________. A. plate separators are grounded B. cell voltages are excessive C. specific gravity in insufficient D. charging rate is excessive
Description : Which of the following statements comparing transistors and vacuum tubes is correct? A. Both transistors and vacuum tubes have a cathode that must be heated to give off electrons. B. A vacuum tube must ... flow. D. The anode of both transistors and vacuum tubes must be heated to give off electrons.
Description : Which of the listed conditions describes the effect on intrinsic semiconductor operation as a result of a temperature increase? A. Additional heat sinks will be required B. Conductivity will increase C. Conductivity will decrease D. Resistivity will increase
Description : If the three-phase motor, shown in the illustrated schematic diagram, is running in the forward direction, which of the following actions must occur before the motor will reverse rotation? EL-0011 A. Normally-closed ... 'L1' and 'L3' must be interchanged via the 'R' contacts. D. All of the above.
Description : In the illustration, the small battery and Rb are in the circuit to apply ________. EL-0022 A. forward bias to the emitter-base B. reverse bias to the emitter-base C. a 'reference charge' on the input capacitor D. a buffer between the input ground and the emitter ground
Description : In the illustration, the large battery and R(L) are in the circuit to ________. EL-0022 A. forward bias the emitter-base B. reverse bias the emitter-base C. forward bias the emitter/collector D. reverse bias the emitter/collector
Description : While testing a semi-conductor diode with an ohmmeter, both the forward and reverse readings are almost in the infinity range. This would indicate that the unit is _____________. A. good B. open C. grounded D. shorted