RWE8 - ELEX
d
1 KVA, 230 V, 50 Hz, single phase transformer has an eddy current loss of 30 watts. The eddy current loss when the transformer is excited by a dc source of same voltage will be a. 30 W b. more than 30 W c. less than 30 W d. zero watt
a
A "U" shaped, opposite-polarity material built near a JFET-channel center is called the: A.gate B.block C.drain D.heat sink
a
A 4 pole dc generator is running at 1500 rpm the frequency of current in the armature winding is a. 50Hz. b. 100Hz. c. 150Hz. d. 200Hz.
a
A 474V, dc shunt motor draws 12A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5Ω and the field winding resistance is 80Ω. The external resistance to be added in the armature circuit to limit the armature current to 125% of its rated value is a. 31.1 Ω b. 15.1 Ω c. 31.6 Ω d. 15.6 Ω
d
A TRIAC: [A].can trigger only on positive gate voltages [B].can trigger only on negative gate voltages [C].cannot be triggered with gate voltages [D].can be triggered by either a positive or a negative gate voltage
c
A basic S-R flip-flop can be constructed by cross-coupling which basic logic gates? A.AND or OR gates B.XOR or XNOR gates C.NOR or NAND gates D.AND or NOR gates
d
A basic series regulator has [A].an error detector [B].a load [C].a reference voltage [D].both an error detector and a reference voltage
d
A comparator is an example of a(n) A.active filter B.current source C.linear circuit D.nonlinear circuit
a
A d.c. shunt generator has full load voltage regulation of 10% at rated speed of 1000 rpm. If it is driven at 1250 rpm, then its voltage regulation at full load would a. be more than 10% b. be less than 10% c. remain unchanged d. be 12.5%
b
A decoder converts ________. A.noncoded information into coded form B.coded information into noncoded form C.HIGHs to LOWs D.LOWs to HIGHs
a
A digital-to-analog converter is an application of the [A].scaling adder [B].voltage-to-current converter [C].noninverting amplifier [D].adjustable bandwidth circuit
a
A logic circuit that provides a HIGH output for both inputs HIGH or both inputs LOW is a(n): A.Ex-NOR gate B.OR gate C.Ex-OR gate D.NAND gate
b
A logic probe is placed on the output of a gate and the display indicator is dim. A pulser is used on each of the input terminals, but the output indication does not change. What is wrong? A.The dim indication on the logic probe indicates that the supply voltage is probably low. B.The output of the gate appears to be open. C.The dim indication is the result of a bad ground connection on the logic probe. D.The gate is a tristate device.
a
A nonvolatile type of memory that can be programmed and erased in sectors, rather than one byte at a time is: A.flash memory B.EPROM C.EEPROM D.MPROM
a
A series of gradually decreasing sine wave oscillations is called: A.ringing B.slew C.overshooting D.undershooting
a
A shunt generator running at 1000 rpm has generated emf of 100 V. If the speed increases to 120 rpm, the generated emf will be nearly a. 120 V b. 175 V c. 140 V d. 240 V
c
A silicon diode measures a low value of resistance with the meter leads in both positions. The trouble, if any, is a. the diode is open. b.the diode is shorted to ground. c.the diode is internally shorted. d.the diode is working correctly.
c
A single transistor can be used to build which of the following digital logic gates? A.AND gates B.OR gates C.NOT gates D.NAND gates
b
A two-pole high-pass active filter would have a roll-off rate of [A].40 dB/decade [B].-40 dB/decade [C].20 dB/decade [D].-20 dB/decade
b
A zero-level detector is a [A].comparator with a sine-wave output [B].comparator with a trip point referenced to zero [C].peak detector [D].limiter
c
Across which of the following components of a power supply does the average (dc) voltage exist? A.Diodes B.Secondary of the transformer C.Capacitor filter D.None of the above
c
An AND gate with schematic "bubbles" on its inputs performs the same function as a(n)________ gate. [A].NOT [B].OR [C].NOR [D].NAND
a
Calculate Bac at VCE = 15 V and IB = 30 uA. (figure 43) [A].100 [B].106 [C].50 [D].400
a
Derive the Boolean expression for the logic circuit shown below: (fig 55) A. C(A+B)DE B. [C(A+B)D+E'] C. [[C(A+B)D]E'] D. ABCDE
c
Derive the Boolean expression for the logic circuit shown below: (fig number 37) [A].CA+CB+CD [B].C(A+B)D' [C].C(A+B)+D [D].CA+CB+D
c
Hexadecimal letters A through F are used for decimal equivalent values from: A.1 through 6 B.9 through 14 C.10 through 15 D.11 through 17
b
How many BCD code bits and how many straight binary bits would be required to represent the decimal number 643? [A].12 BCD, 12 binary [B].12 BCD, 10 binary [C].12 BCD, 9 binary [D].16 BCD, 9 binary
c
How will a D-MOSFET input impedance change with signal frequency? A.As frequency increases input impedance increases. B.As frequency increases input impedance is constant. C.As frequency decreases input impedance increases. D.As frequency decreases input impedance is constant.
d
If a transistor operates at the middle of the dc load line, a decrease in the current gain will move the Q point: [A].off the load line [B].nowhere [C].up [D].down
c
If the input to a comparator is a sine wave, the output is a: A.ramp voltage B.sine wave C.rectangular wave D.sawtooth wave
d
If the value of resistor Rf in an averaging amplifier circuit is equal to the value of one input resistor divided by the number of inputs, the output will be equal to [A].the average of the individual inputs [B].the inverted sum of the individual inputs [C].the sum of the individual inputs [D].the inverted average of the individual inputs
a
Implementing the expression AB + CDE using NAND logic, we get: A.(A) B.(B) C.(C) D.(D) (see fig number 33)
a
In a C-E configuration, an emitter resistor is used for: A.stabilization B.ac signal bypass C.collector bias D.higher gain
c
In an averaging amplifier, the input resistances are [A].equal to the feedback resistance [B].less than the feedback resistance [C].greater than the feedback resistance [D].unequal
a
In the classic three-op-amp instrumentation amplifier, the differential voltage gain is usually produced by the A.first stage B.second stage C.mismatched resistors D.output op-amp
d
In the decimal numbering system, what is the MSD? a. The middle digit of a stream of numbers b. The digit to the right of the decimal point c. The last digit on the right d. The digit with the most weight
a
In which of the following applications is a pulsating dc voltage suitable? A.Battery charger B.Radio C.Stereo system D.Computer
b
Initially, the closed-loop gain (Acl) of a Wien-bridge oscillator should be A.Acl < 3 B.Acl > 3 C.0 D.Acl≅1
b
JFET terminal "legs" are connections to the drain, the gate, and the: A.channel B.source C.substrate D.cathode
b
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
c
Once a DIAC is conducting, the only way to turn it off is with: A.a positive gate voltage B.a negative gate voltage C.low-current dropout D.breakover
d
One application of a digital multiplexer is to facilitate: A.data generation B.serial-to-parallel conversion C.parity checking D.data selector
d
Refer to the figure given below. The probable trouble, if any, indicated by these voltages is (see fig 47) A.one of the diodes is open. B.a diode is shorted. C.an open transformer secondary. D.the filter capacitor is shorted.
d
Refer to the given figure. This circuit is a setup for (see fig 39) A.an antilog amplifier. B.a constant-current source. C.an instrumentation amplifier. D.an isolation amplifier.
a
Refer to this figure. If VIN increases, IZ will [A].increase. [B].decrease. [C].remain the same. [D].either A or B (see fig 35)
b
Schottky diodes are also known as [A].PIN diodes. [B].hot carrier diodes. [C].step-recovery diodes. [D].tunnel diodes.
c
Single-element semiconductors are characterized by atoms with ____ valence electrons. a. 3 b. 5 c. 4 d. 2
a
The 7805 regulator IC provides ________. A.5 V B.-5 V C.12 V D.-12 V
a
The C-B configuration is used to provide which type of gain? A.voltage B.current C.resistance D.power
a
The PUT (programmable unijunction transistor) is actually a type of: [A].UJT thyristor [B].FET device [C].TRIAC [D].SCR
b
The access time (tacc) of a memory IC is governed by the IC's: A.internal address buffer B.internal address decoder C.volatility D.internal address decoder and volatility
c
The basic logic gate whose output is the complement of the input is the: A.OR gate B.AND gate C.INVERTER gate D.comparator
d
The center frequency of a band-pass filter is always equal to the a. bandwidth b. -3 dB frequency c. bandwidth divided by Q d. geometric average of the critical frequencies
a
The commutative law of addition and multiplication indicates that: A.the way we OR or AND two variables is unimportant because the result is the same B.we can group variables in an AND or in an OR any way we want C.an expression can be expanded by multiplying term by term just the same as in ordinary algebra D.the factoring of Boolean expressions requires the multiplication of product terms that contain like variables
c
The formula Ic=(Vc/t)C shows that for a given capacitor, if the voltage changes at a constant rate with respect to time, the current will [A].increase [B].decrease [C].be constant [D].decrease logarithmically
d
The input/output relationship of the common-collector and common-base amplifiers is: A.270 degrees B.180 degrees C.90 degrees D.0 degrees
c
The output will be a LOW for any case when one or more inputs are zero in a(n): A.OR gate B.NOT gate C.AND gate D.NAND gate
a
The primary function of the oscillator in an isolation amplifier is to A.convert dc to high-frequency ac B.convert dc to low-frequency ac C.rectify high-frequency ac to dc D.produce dual-polarity dc voltages for the input to the demodulator
b
The six basic forms of energy are: A.light, sun, magnetic, chemical, electrical, and mechanical B.electrical, mechanical, light, heat, magnetic, and chemical C.electrical, mechanical, sun, heat, chemical, and light D.potential, sun, light, chemical, electrical, and mechanical
d
The smallest amount of current that the cathode-anode can have, and still sustain conduction of an SCR is called the: A.maximum forward current B.maximum forward gate current C.holding current D.reverse gate leakage current
a
The switching speed of CMOS is now ________. A.competitive with TTL B.three times that of TTL C.slower than TTL D.twice that of TTL
c
The systematic reduction of logic circuits is accomplished by: A.symbolic reduction B.TTL logic C.using Boolean algebra D.using a truth table
c
The term bias in electronics usually means A.the value of ac voltage in the signal. B.the condition of current through a pn junction. C.the value of dc voltages for the device to operate properly. D.the status of the diode.
c
The time needed for a pulse to increase from 10% to 90% of its amplitude defines: A.pulse width B.propagation delay C.rise time D.duty cycle
c
The time needed for an output to change as the result of an input change is known as: A.noise immunity B.fanout C.propagation delay D.rise time
b
The type of bias most often used with E-MOSFET circuits is: A.constant current B.drain-feedback C.voltage-divider D.zero biasing
a
This circuit is a ________ oscillator. (fig 63 three parallel rc) A.phase-shift B.Wien bridge C.Colpitts D.Hartley
c
Three different Q points are shown on a dc load line. The upper Q point represents the: [A].minimum current gain [B].intermediate current gain [C].maximum current gain [D].cutoff point
b
To operate properly, a transistor's base-emitter junction must be forward biased with reverse bias applied to which junction? [A].collector-emitter [B].base-collector [C].base-emitter [D].collector-base
b
Under normal conditions a diode conducts current when it is [A].reverse-biased. [B].forward-biased. [C].avalanched. [D].saturated.
b
Voltage-divider bias provides: A.an unstable Q point B.a stable Q point C.a Q point that easily varies with changes in the transistor's current gain D.a Q point that is stable and easily varies with changes in the transistor's current gain
c
What are the two main applications for ac? A.direct, pulsating B.electric, magnetic C.power, information D.static, dynamic
a
What are the two types of adder circuits? a. half adder and full adder b. half adder and parallel adder c. asynchronous and synchronous d. one's complement and two's complement
d
What is the frequency of rotor current of 50hz induction motor operating at 4% slip? a. 50 Hz b. 1 Hz c. 2.5 Hz d. 2 Hz (not sure)
c
What is the purpose of an additional RC filter section in a power supply circuit? [A].Increase the dc voltage component [B].Increase the ac voltage component [C].Decrease the ac voltage component [D].None of the above
a
What is the ratio of the peak ripple voltage level to its rms voltage level? A. √3 B. √2 C. √(3/2) D. √(2/2)
a
What is the typical value of quality factor for crystal oscillators? A.20,000 B.1000 C.100 D.10
d
When an input signal reduces the channel size, the process is called: A.enhancement B.substrate connecting C.gate charge D.depletion
b
When both inputs of a J-K flip-flop cycle, the output will: A.be invalid B.not change C.change D.toggle
a
When checking a good SCR or TRIAC with an ohmmeter it will: A.show high resistance in both directions B.show low resistance with positive on anode and negative on cathode, and high resistance when reversed C.show high resistance with negative on anode and positive on cathode, and low resistance when reversed D.show low resistance in both directions
c
When not in use, MOSFET pins are kept at the same potential through the use of: A.shipping foil B.nonconductive foam C.conductive foam D.a wrist strap
d
When using an OTA in a Schmitt-trigger configuration, the trigger points are controlled by [A].the Iout [B].the IBIAS [C].the Vout [D].both Iout and IBIAS
b
Which application best describes this 555 timer circuit? (see fig 51) A.Monostable multivibrator B.Astable multivibrator C.Bistable multivibrator D.One-shot multivibrato
b
Which circuit is known as a voltage-to-current converter? (see fig 78) a. a b. b c. c d. d
a
Which diode arrangement will supply a positive output voltage? (fig 56) A.a B.b C.c D.d
b
Which element dictates the maximum level of source voltage? (see figure 44) [A].VZ [B].IZM [C].IZ [D].None of the above
d
Which is the most important step utilized when measuring resistors? A.use the highest possible scale B.keep test leads short C.zero the meter before using D.remove power from the circuit
d
Which of the following improvements is (are) a result of the negative feedback in a circuit? A.Lower output impedance B.Reduced noise C.More linear operation D.All of the above
d
Which of the following is (are) feedback? A.Voltage-series B.Voltage-shunt C.Current-series D.All of the above
a
Which of the following is a semiconductor memory? [A].RAM [B].MAR [C].CD-ROM [D].CD
a
Which of the following is correct for a gated D-type flip-flop? A.The Q output is either SET or RESET as soon as the D input goes HIGH or LOW. B.The output complement follows the input when enabled. C.Only one of the inputs can be HIGH at a time. D.The output toggles if one of the inputs is held HIGH.
d
Which of the following is not a basic Boolean operation? A.OR B.NOT C.AND D.FOR
d
Which of the following should be done to obtain the ac equivalent of a network? A.Set all dc sources to zero B.Replace all capacitors by a short-circuit equivalent. C.Remove all elements bypassed by the short-circuit equivalent. D.All of the above
a
Which of the following statements does NOT describe an advantage of digital technology? [A].The values may vary over a continuous range. [B].The circuits are less affected by noise. [C].The operation can be programmed. [D].Information storage is easy.
d
Which test equipment best allows a comparison between input and output signals? A.an oscilloscope B.a logic probe C.a spectrum analyzer D.a multitrace oscilloscope
c
With a complex circuit, a supply source senses: A.open circuit components B.when voltages need to be increased C.only a single resistive connection D.when complex currents are needed
b
With low-power transistor packages, the base terminal is usually the: A.tab end B.middle C.right end D.stud mount
