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WorksheetsCET Section III
Total questions: 75
Worksheet time: 38mins
Name
Class
Date
1.
When looking at waveforms in a switching power supply which of the following should not be done?
a)
look at waveforms in the primary circuit and the secondary circuit with one probe and with its ground lead connected to the respective ground
b)
look at the control signal of the switching device
c)
connect one probe ground lead to hot ground and the other to cold ground
d)
vary the input AC voltage
2.
What Vcc should be observed in TTL circuits?
a)
3 V to 15 V
b)
5 V
c)
12 V
d)
+/- 15 V
3.
If a unit under test is dead what is the most logical area to check first?
a)
the power supply
b)
the output device
c)
divide the unit in half and begin in the middle
d)
begin at the input and trace to the output
4.
To look at a high frequency, high magnitude waveform across a component(s), neither side of which is at chassis common, the oscilloscope would be used:
a)
in the AC coupling mode
b)
in the DC coupling mode
c)
in the invert/add mode
d)
by plugging the oscilloscope into an isolation transformer
5.
If a defective Hall-effect sensor is suspected check:
a)
the continuity of the coil in the device
b)
that current is being supplied to the device
c)
that the window in the device is not dirty and light is being blocked
d)
that the internal magnetic bias in the sensor is strong enough
6.
Refer to Figure 1. The output of this circuit will be:
a)
nearly the same pp signal as the input with the opposite phase
b)
nearly the same pp signal as the input with the same phase
c)
a larger pp signal than the input with the opposite phase
d)
a larger pp signal than the input with the same phase
7.
On the schematic of the unit you are testing you note that the word reset on the microprocessor has an overbar. The condition on that pin, at power up would be expected to be:
a)
low and stay low
b)
high and stay high
c)
low and then go high
d)
high and then go low
8.
What happens when a sine wave signal is input to a non-inverting op-amp circuit if the feedback resistor is open?
a)
no observable symptom
b)
reduced output
c)
output at only positive and negative saturation
d)
an overheated op-amp
9.
If a diode in a bridge rectifier opens, the observable symptom is:
a)
no observable symptom
b)
increased ripple and decreased dc output under load
c)
the opposite diode in the bridge will fail
d)
the primary fuse will be blown
10.
What might be used in a triac circuit to lessen the chance of turn on by a sharp increase in the off-state voltage.
a)
a snubber
b)
a varactor
c)
a metal oxide varistor
d)
a kick back diode
11.
What indication is observed when ohmmeter testing a good fuse?
a)
a very low resistance
b)
infinite resistance
c)
low resistance in one direction and high resistance in the other direction
d)
approximately 1K ohms in both directions
12.
If a transistor in Class A amplifier is replaced and the emitter and collector leads of the replacement are accidentally reversed, the most likely consequence would be:
a)
a burned collector resistor
b)
a burned emitter resistor
c)
both 1 and 2
d)
a gain that is less than normal
13.
The operating frequency of a normally loaded switching power supply might be about:
a)
60 Hz
b)
120 Hz
c)
1 kHz
d)
70 kHz
14.
With the conditions as shown in Figure 2, the output should be seen as:
a)
a high
b)
a low
c)
pulsing
d)
a high impedance
15.
If the op-amp circuit in Figure 3 is working properly and is powered with +/- 9 V, the signal voltage at point X should be:
a)
0 V
b)
0.7 V
c)
9 V
d)
18 V
16.
What resistance indications should be obtained when testing a functional diode with an analog meter having sufficient voltage at its terminals?
a)
low resistance in both directions
b)
high resistance in both directions
c)
high resistance in one direction and low resistance in the other
d)
no indication since an analog meter generally will not turn on a diode junction.
17.
The indications shown on Figure 4 were obtained using a logic probe. What conclusion can be drawn from these indications?
a)
the circuit is functioning properly
b)
the circuit is probably functioning properly but, an oscilloscope test is necessary to confirm this
c)
the circuit is not functioning properly
d)
the circuit is probably not functioning properly, but an oscilloscope test is necessary to confirm this
18.
Which components are most susceptible to damage by static discharge?
a)
bipolar transistors
b)
TTL ICs
c)
MOS ICs
d)
fast blow fuses
19.
A 60 Hz signal found everywhere in a circuit when using an oscilloscope usually means:
a)
there is a shorted diode in the power supply
b)
the scope should be switched to dc coupling
c)
there is a bad scope lead ground
d)
the outlet the unit is plugged into is wired incorrectly
20.
What logic level would be represented by 1.5 volts in a TTL circuit?
a)
high
b)
low
c)
tristate
d)
an invalid logic level
21.
If the circuit of Figure 5 is functioning correctly and a 10 mVpp sine wave is connected to C1 the waveform at the emitter should be:
a)
about 10 mVpp
b)
about the same amplitude as the signal on the collector
c)
too small to measure
d)
approximately β times the base signal
22.
If the amplifier in Figure 5 is a Class A amplifier and is biased correctly for maximum undistorted sine wave output, the DC voltage on the collector should be about:
a)
0 V
b)
2.5 V
c)
5.0 V
d)
10.0 V
23.
In Figure 5, about how much emitter current would be expected?
a)
0 mA
b)
1 mA
c)
7 mA
d)
there is not enough information given to calculate
24.
Which of the following ohmmeter tests should never give a low resistance reading when out of circuit testing an NPN transistor?
a)
emitter to base
b)
emitter to collector
c)
base to collector
d)
base to emitter
25.
How is the voltmeter connected to measure the voltage developed by the current through a component?
a)
in series with the component
b)
in parallel with the component
c)
by removing the component and replacing it with the voltmeter
d)
by momentarily opening the component and measuring its voltage
26.
An ohmmeter test across the anode-cathode (positive lead to anode and negative lead to cathode and with the gate unconnected) of an out of circuit SCR shows low resistance. What would you conclude?
a)
it is defective, probably shorted
b)
that junction is all right
c)
it is a good SCR
d)
cannot make final conclusion until a power test is performed
27.
When using an oscilloscope to closely examine the rise or fall time of a signal, which of the following would be used?
a)
a slow sweep speed
b)
the alternate mode
c)
the chopped mode
d)
the delayed sweep mode
28.
What precautions should be taken when using an oscilloscope to make hot chassis measurements?
a)
no precautions are necessary
b)
the technician should wear a ground strap
c)
hot components should be removed with grounded soldering tools
d)
the unit under test should be powered through an isolation transformer
29.
Which instrument must always be used with the power off in the circuit under test?
a)
voltmeter
b)
ohmmeter
c)
ammeter
d)
frequency counter
30.
A switching power supply should initially be tested:
a)
unloaded
b)
loaded
c)
at reduced input voltage
d)
by reducing the main power frequency
31.
The input impedance of an oscilloscope is generally:
a)
very low
b)
very high
c)
adjustable with the triggering source control
d)
adjustable with the triggering level control
32.
Which AC voltage measurement is generally provided by handheld, inexpensive, service quality digital multimeters?
a)
peak
b)
peak to peak
c)
effective
d)
true average
33.
What is the approximate frequency of a waveform displayed on an oscilloscope when a period spans 5.2 horizontal gradicules and the sec/div setting is 10 microseconds?
a)
.019 Hz
b)
19 Hz
c)
19 kHz
d)
19 MHz
34.
The compensation adjustment of an oscilloscope probe is usually performed when displaying a:
a)
random noise signal
b)
square wave
c)
sine wave
d)
triangular wave
35.
When using the X10 on the sweep speed control (sec/div) the technician must:
a)
multiply the volts/div reading by 10
b)
divide the volts/div reading by 10
c)
multiply the sec/div reading by 10
d)
divide the sec/div reading by 10
36.
Which of the following ammeter impedances provides for the least amount of circuit intrusion?
a)
0.1 ohms
b)
10 ohms
c)
100 ohms
d)
1K ohms
37.
When an oscilloscope is used in the normal trigger mode, which control is adjusted to start the sweep?
a)
trigger source
b)
trigger level
c)
volts/div
d)
vertical coupling
38.
Which of the following is not indicated by a logic probe?
a)
a voltage in the logic high region
b)
a voltage in the logic low region
c)
a voltage in the indeterminate region
d)
the magnitude of a voltage in the indeterminate region
39.
When used for making voltage measurements, which of the following voltmeter input impedances provides for the least amount of circuit loading?
a)
10K ohms
b)
100K ohms
c)
10 M ohms
d)
the impedance of the meter does not determine loading
40.
Observation of two low frequency signals of approximately 50 Hz on a dual trace oscilloscope may best be done by the use of the:
a)
dual time base mode
b)
expanded mode
c)
alternate mode
d)
chopped mode
41.
What kind of two input device produces a HIGH output only when the inputs are different?
a)
NAND gate
b)
NOR gate
c)
XOR gate
d)
XNOR gate
42.
When a number of signals are connected to a common bus, a tristate buffer might be used to:
a)
improve fan-out
b)
interface different types of IC
c)
condition slow signal transition time
d)
prevent bus contention
43.
A two input gate which has a LOW output with all possible input conditions except when both are LOW is a/an:
a)
AND
b)
NAND
c)
OR
d)
NOR
44.
The circuit in Figure 6, represents a basic:
a)
oscillator
b)
differentiator
c)
integrator
d)
Schmitt trigger
45.
A chip resistor which has ‘470’ stamped on it means that its value is:
a)
0.47 ohms
b)
4.7 ohms
c)
47 ohms
d)
470 ohms
46.
When the output of one TTL device, which is connected to the input of another device, is LOW that output is said to be:
a)
asserted
b)
unasserted
c)
current sinking
d)
current sourcing
47.
What is the output voltage of the circuit in Figure 7?
a)
0 V
b)
0.7 V
c)
2.0 V
d)
5.0 V
48.
In Figure 8, the output voltage will be:
a)
Vz + 0.7 V
b)
Vz - 0.7 V
c)
Vz
d)
Vin - Vz
49.
What function does the optocoupler serve in a solid state relay (SSR)?
a)
power switch
b)
fuse
c)
isolation
d)
optocouplers are not found in SSRs
50.
With an asserted level on clear and an unasserted level on set, if the J input of a JK flip flop is high and the K input is high, what is the Q output after the next clock pulse?
a)
high
b)
low
c)
tristate
d)
the opposite of its pre-clock state
51.
In Figure 9, if C3 opens:
a)
the transistor will be subjected to high current
b)
the gain of the amplifier will increase
c)
the gain of the amplifier will decrease
d)
the transistor will go into cutoff
52.
In Figure 9, if R1 opens:
a)
the negative excursions of the output will be clipped
b)
the positive excursions of the output will be clipped
c)
the collector dc voltage will go down
d)
the collector dc voltage will go up
53.
How is the collector-base junction of a transistor biased during normal common emitter class A operation?
a)
forward
b)
reverse
c)
reverse or forward, respectively, depending whether NPN or PNP
d)
biasing of this junction is unimportant in this case
54.
A zener diode, when used in a voltage regulator circuit, is operated in which mode?
a)
forward biased
b)
reverse biased
c)
forward or reversed biased depending on the polarity of the regulated voltage
d)
at the forward avalanche point
55.
The symbol in Figure 10 is that of a/an:
a)
N-channel depletion-type MOSFET
b)
P-channel depletion-type MOSFET
c)
N-channel enhancement-type MOSFET
d)
P-channel enhancement-type MOSFET
56.
A varactor diode:
a)
is used to emulate a variable resistor
b)
is normally operated in forward bias
c)
depends on its depletion area for its function
d)
is used to emulate a variable inductor
57.
JFETs:
a)
are bipolar transistors
b)
have very low input impedance
c)
are current controlled devices
d)
are voltage controlled devices
58.
A triac:
a)
is not susceptible to off-state voltage turn on as long as the peak voltage does not exceed the voltage breakover point
b)
is a three terminal device with a main terminal 1, a main terminal 2 , and a base.
c)
can be fired with a positive trigger pulse only when the main terminal 1 is positive in respect to the main terminal 2
d)
can be fired with a positive or negative trigger pulse when the main terminal 1 is negative in respect to the main terminal 2
59.
About how much voltage would be dropped across a forward biased silicon diode?
a)
.25 V
b)
.3 V
c)
.7 V
d)
the entire DC source voltage
60.
Which of the following is most true of an SCR?
a)
once fired the gate current must be interrupted to stop conduction
b)
once fired the only way to stop conduction is to reverse the polarity on the gate
c)
an SCR is a bidirectional device which can be fired by high transients on the supply lead
d)
an SCR can be turned on by exceeding the forward breakover voltage
61.
What is the approximate inductive reactance of a 10 mH inductor in a 3.58 MHz circuit?
a)
0.000004 ohms
b)
35.8K ohms
c)
112K ohms
d)
225K ohms
62.
What is the impedance of the circuit of Figure 11?
a)
25 ohms
b)
50 ohms
c)
56 ohms
d)
75 ohms
63.
What is the RMS voltage of a 10 Vpp sine wave?
a)
0.354 V
b)
3.54 V
c)
0.707 V
d)
7.07 V
64.
Which component generally tends to pass high frequencies and block low frequencies?
a)
switch
b)
resistor
c)
inductor
d)
capacitor
65.
What is the resonant frequency of the circuit of Figure 12?
a)
159 Hz
b)
1000 Hz
c)
6200 Hz
d)
7400 Hz
66.
Generally, in a DC circuit, if the voltage supplied to the circuit increases, the current flowing in the circuit:
a)
decreases
b)
increases
c)
stays the same
d)
cannot be generalized without knowing the frequency
67.
How much current is flowing through R3 of Figure 13?
a)
0.00025 A
b)
0.0005 A
c)
0.0010 A
d)
0.0050 A
68.
What is the voltage drop across R3 of Figure 13?
a)
2 V
b)
5 V
c)
10 V
d)
the voltage drop cannot be determined
69.
Approximately how much voltage is dropped across a 15K ohms resistor that is in series with a 30K ohms resistor, when 10 volts is applied to the series circuit?
a)
3.3 V
b)
5 V
c)
6.6 V
d)
10 V
70.
How much resistance does the battery see in the circuit in Figure 14?
a)
2.5K ohms
b)
6K ohms
c)
10K ohms
d)
40K ohms
71.
The Xc of a 0.47 uF capacitor at 2 kHz is about:
a)
16.9 ohms
b)
169 ohms
c)
1693 ohms
d)
16.9K ohms
72.
A current of 250 uA through a 47K ohms resistor will produce a voltage drop of:
a)
11.75 pV
b)
11.75 uV
c)
11.75 mV
d)
11.75 V
73.
When a 10K ohms resistor is connected in series with a parallel combination of two 10K ohms resistors the total resistance across the three becomes about:
a)
333 ohms
b)
3333 ohms
c)
15K ohms
d)
30Kohms
74.
What is the frequency of a sine wave which has a period of 100 us?
a)
10 kHz
b)
100 kHz
c)
1000 kHz
d)
10 MHz
75.
The XL of a 10 mH choke at 1000 kHz is about:
a)
63 ohms
b)
31K ohms
c)
63K ohms
d)
15.9 M ohms
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