Experiment of Electrical Technology - 中国大学mooc
Chapter 1 Introduction
Chapter Test
1、The safety voltage for continuous contact with human body is not higher than () V, and the safety current is not higher than () mA.
A、12, 5
B、24, 10
C、36, 15
D、48, 20
2、In order to improve the effectiveness of classroom experiments, which of the following items shall be done: ()
A、Before the experiment, a measurement data sheet should be designed and the number and interval of measuring points reasonably selected. If the data to be measured is on the curved part of a curve, more measuring points should be arranged whereas fewer points are required on the smooth part. In this way, better results can be obtained from curve fitting in subsequent data processing.
B、Continuity test shall be conducted on the conductor before overlapping the circuit.
C、Usually, the "loop connection method" is adopted through sequential wiring from the power supply until the whole circuit is completed.
D、For a more complex circuit, it shall be divided into several independent sub-circuits according to its functions and completed step by step.
3、In the experiment class, which of the following measures shall be taken to protect against electric shock: ()
A、Do not place drinks, cups and other items on the experiment table.
B、Do not touch experiment devices, instruments and equipment with wet hands.
C、Connect the circuit on an insulation pad carefully according to the circuit diagram, and check it after it is connected. If necessary, ask the teacher to recheck it to ensure that it is correct before switching on the power supply. If it is necessary to change or disconnect the line during the experiment, cut off the power supply before performing any operation.
D、If any abnormal phenomena arise during the experiment such as heating, luminescence, sound and smell, cut off the power supply immediately, report to the teacher and identify the cause to prevent failure propagation.
4、In the experiment class, in case of an electric shock accident, which of the following measures shall be taken: ()
A、The first thing is to ensure the safety of the rescuers themselves.
B、Then disconnect the person who gets an electric shock from the power supply. The most effective way to do this is to directly close the switch and cut off the power supply.
C、Insulating objects such as dry wooden sticks shall be used to separate the electric shock victim from the power source.
D、Call the 120 first-aid phone number at once and adopt artificial respiration in case of emergency. Then call Beihang University Alarm Center at 82317119.
5、The main causes of electric fires include: ()
A、Electric leakage
B、Short circuit
C、Excess load
D、Excessive contact resistance
6、Which of the following shall be used for extinguishing electric fire: ()
A、Water
B、Carbon-dioxide (fire) extinguisher
C、Foam fire extinguisher
D、Powder fire extinguisher
Chapter 2 Common Instruments
Chapter Test
1、What factors shall be considered when selecting instruments? ()
A、Accuracy of instruments.
B、Impedance of instrument.
C、Frequency range of instrument.
D、All of the above shall be considered.
2、Which wiring method shall be selected to measure 10kΩ resistance using TH1941 digital multimeter? ()
A、![]()
B、![]()
C、![]()
D、All of the above methods are OK.
3、Which system shall be adjusted to stably display the measured waveform on the oscilloscope? ()
A、Vertical system.
B、Horizontal system.
C、Triggering system.
D、All of the above shall be adjusted.
4、Which methods could be used for measuring signal amplitude with a digital oscilloscope? ()
A、Calculation of grid number.
B、CURSOR measurement method.
C、MEASURE measurement method.
D、All of the above methods are OK.
5、Using digital oscilloscope to observe the waveform of DC signal, which coupling method shall be selected for the measurement channel? ()
A、DC coupling.
B、AC coupling.
C、Grounding.
D、All of the above are acceptable.
6、Which two terminals shall be selected when MPS-3003LK-3 DC stabilized power supplies is used to output +12V? ()![]()
A、1, 3
B、2, 3
C、4, 5
D、All of the above are acceptable.
7、The signal output of the function signal generator can be short circuited. ()
Chapter 3 Circuit Design and Simulation
Chapter Test
1、When using Proteus software to control the visual field of the editing area, press keys F5 (), F6 (), F7 (), F8 (). (1) Reduce. (2) Amplify. (3) Display the whole drawing. (4) Display a graph centered on the mouse pointer. The correct order should be: ()
A、(1), (2), (3), (4).
B、(4), (2), (1), (3).
C、(1), (3), (2), (4).
D、(4), (1), (2), (3).
2、When using an oscilloscope to observe signals, the trigger function plays an important role in stabilizing the signal waveform, and the trigger level shall generally be adjusted to: ()
A、The middle of the observation area.
B、The peak of the observation signal.
C、Within the amplitude range of the observed waveform.
D、The valley of the observation signal.
3、During the "common-emitter amplifier" simulation test, the Quiescent point can be adjusted by using: ()
A、Voltage probe
B、Current probe
C、AC voltmeter
D、DC voltmeter
4、When using Proteus software, it is necessary to check the electrical rules after connecting the circuit. ()
5、When using Proteus software, click "Run Simulator by Dynamic Frame" to facilitate single-step operation and observe the simulation process. ()
6、When using a probe to test current, it is required that the arrow of current probe be perpendicular to the conductor, otherwise an error will be reported. ()
7、During the "common-emitter amplifier" simulation test, dynamic parameters shall be measured while ensuring the output waveform is not distorted. ()
Chapter 4 Remote Online Circuit Experiment
Chapter Test
1、In the software interface of the remote online experiment platform, click "Scan" to display the modular components which have been furnished on the current experiment platform.
2、In the software interface of the remote online experiment platform, click "Find Instrument" to display the required instrument and equipment list, and this indicates that the instruments are successfully connected.
3、In the remote online experiment, the circuit is created. If there are key errors in the wiring, the system will check and find them so as to avoid issuing the circuit to cause damage.
4、In the remote online experiment, every time the circuit connection is modified, it is necessary to click "Issue" again and then click "Refresh Measurements" to ensure that the measurements are consistent with the actual situation.
5、In the software of the remote online experiment platform, check the required test items and click "Refresh Measurements" to update the results continuously.
6、In the software of the remote online experiment platform, "Waveform Screenshot" displays the test results of all test items on CH1 on the basis of recording two channel’s waveforms.
Chapter 5 Construction and Measurement of DC Circuit
Chapter Test
1、Which of the following are non-linear elements?
A、Resistance
B、Inductance with iron core
C、Field effect tube
D、Diode
2、The circuit "Ground” is signal "Ground", also known as the “Reference Ground", which is the zero-potential reference point. Which of the following signals should be connected to the "Ground" terminal when conducting the circuit "Common Ground” measurement?
A、Power supply ground
B、Black clamp of O-scope probe cable
C、Black clamp of signal generator probe cable
D、Amplifier circuit ground
E、Multimeter black test lead
3、In the circuit, the linear element's current is proportional to the voltage, the volt-ampere charac. curve is a straight line passing through the origin of coordinate, and Ohm's law applies to the linear element. Except for some ordinary resistors, the daily used components are basically linear components.
4、In this experiment, when testing the volt-ampere characteristics of voltage-adjustable signal source, by changing the load resistance to change the loop current, the corresponding output voltage can be measured, and then the internal resistance of the power supply can be calculated.
5、In this experiment, when testing the output characteristics of voltage-adjustable signal source, a fixed resistor is added to the bleeder circuit. According to the circuit’s needs, this resistor can be omitted in general.
6、In the experiment of the R/2R shunt circuit, the voltage division is achieved through branch shunt.
7、When measuring the current, it is necessary to connect an ammeter (or an multimeter in current mode) in series to the branch to be measured. In electronic circuits, indirect measurement is often used. By connecting a relatively small resistance in series to a branch, that is, to measure the voltage across a known resistance with a voltmeter, and then determine the current value.
8、For connection of experimental circuit, the loop method is often used, which generally starting from the positive pole of a power supply, and connect one loop after another. For the following R/2R shunt circuit, the circuit wiring sequence can be: 1-2-3-4，2-5-6-7-8-3，7-9-10-11-12-8，11-13-14-15-16-12，15-17-18-16
Chapter 6 Attenuator & RC Low-pass Filter
Chapter Test
1、For the low-pass filter as shown in the figure, the corner frequency is:![]()
A、![]()
B、![]()
C、![]()
D、![]()
2、As shown in the figure, connect an attenuator between the signal source and the load RL. At this point, the power obtained by the load is 1% of that when the signal source and the load are directly connected, then the relationship between U1 and U2 should be:![]()
A、U1 =2U2
B、U1 =5U2
C、U1 =10U2
D、U1 =100U2
3、Which of the following description of measuring frequency characteristics by the dot frequency measurement method is incorrect?
A、In the process of measurement, attention should be paid to the output signal to ensure no distortion.
B、Near the corner point, the measurement frequency points should be denser.
C、Select the test frequency points uniformly in the frequency range.
D、The abscissa of amplitude-frequency curve generally adopts logarithmic coordinate, and the test frequency is selected according to logarithmic law.
4、Frequency characteristic measurement includes amplitude-frequency and phase-frequency characteristic measurements.
5、A filter is used to intercept the signal according to the required frequency band, including high-pass filter, low-pass filter, band-pass filter, band-elimination filter and so on.
6、Any passive linear two-port network can be equivalent to a two-port network composed of three impedances.
Chapter 7 Coil Parameter Measurement and Three-phase Circuit
Chapter Test
1、After connecting a capacitor in parallel at both ends of the inductive load, the circuit’s average power:
A、Increases
B、Decreases
C、Remains unchanged
D、Is unknown
2、In the three-phase circuit, which of the following description of the neutral line is incorrect?
A、The neutral line can make each phase independent, and the work of each phase does not affect each other.
B、In the case of asymmetric load, the neutral line can play a role in ensuring safe power supply.
C、In a symmetrical three-phase circuit, the neutral line current is 0.
D、In an asymmetrical three-phase circuit, the neutral line current is 0.
3、The inductance of both air-core and iron-core coil are constant at low frequencies.
4、Connecting a capacitor in parallel at both ends of the inductive load can improve the power factor.
5、In the experiment, when the power is turned on and off, the measuring instrument should not be connected to the circuit.
6、Connecting a capacitor in parallel at both ends of the inductive load can improve the power factor, and the larger the capacitance is, the larger the power factor will be.
Chapter 8 A Circuit’s Frequency Characteristics and Square Wave Response
Chapter Test
1、Regarding the oscilloscope, which of the following statements is correct?
A、An oscilloscope can only be used to observe the waveform of voltage signal
B、There are only two measurement methods for digital oscilloscope waveform parameters: counting of grid number and cursor-assisted measurement method
C、An oscilloscope can be used to directly observe the waveform of current
D、An oscilloscope usually has 2 working modes: Y-T and X-Y modes
2、After turning on the O-scope’s power, the reason that the scan line does not appear on the screen at the beginning may be:
A、The horizontal or vertical displacement of CH1 or CH2 is incorrect ("beyond" the screen)
B、The screen brightness is adjusted too dark
C、The trigger source is incorrectly selected
D、The X-Y mode is used
3、The reason that a scope-displayed waveform is unstable may be:
A、The trigger source is incorrectly selected
B、The Sensitivity knob is improperly adjusted
C、The X-Y mode is used
D、The trigger level is not adjusted well
4、Use an oscilloscope to simultaneously observe two signals of different frequencies. By which of the following methods are the waveform generally easy to adjust and stabilize?
A、Use the channel with the high frequency signal as the trigger source
B、Use the channel with the low frequency signal as the trigger source
C、Adjust the trigger level line to fall within the range of low-freq. signal waveform
D、Adjust the trigger level line to fall within the range of high-freq. signal waveform
5、What issues should be attended to when two channels of an oscilloscope are being used?
A、Any position can be arbitrarily observed on two channels, by the same method as one channel is used alone.
B、When two channels of an oscilloscope are simultaneously used, the two black clamps should be connected together, or only one of them should be used and the other dangling.
C、When two channels of an oscilloscope are simultaneously used, the two black clamps should be connected together before connecting to the circuit “Ground”.
D、When two channels of an oscilloscope are simultaneously used to observe the circuit waveforms, there should be no components connected between the two black clamps.
Chapter 9 TTL and CMOS Gate Circuits
Chapter Test
1、In TTL and CMOS interconnection experiments, based on oscilloscope waveforms the TTL rise rate can be calculated as (), and CMOS rise rate as (). ()![]()
A、32ns, 118ns
B、131.25V/us, 27.1V/us
C、118ns, 32ns
D、27.1 V/us, 131.25 V/us
2、When testing the voltage transmission characteristics of TTL NAND gate (74LS00), the input signal is 500Hz (), and () mode shall be selected when observing the oscilloscope waveform. ()
A、Sinusoidal Wave, Y-T.
B、Sawtooth wave, X-Y.
C、Sinusoidal Wave, X-Y.
D、Sawtooth wave, Y-T.
3、TTL NAND gate opening level UON refers to the input level when the output level has just dropped to the upper limit of the output low level. It is the maximum input high level value allowed to ensure the output of NAND gate is low level (); the closing level UOFF refers to the input level when the output level has just risen to the lower limit of the output high level. It is the minimum input low level value allowed to ensure the output of NAND gate is high level. ()
4、The redundant or temporarily unused input terminals of TTL circuit cannot be suspended. For TTL NAND gate, the unused input terminals can be connected in parallel or directly to high level. For TTL NOR gate, unused input terminals can be connected in parallel or directly to low level. ()
5、CMOS chips generally have a protecting circuit inside. In order for the protecting circuit to work, the chip power supply shall be switched on before adding an external signal source. After completion, the signal source shall be switched off before the power supply is turned off. ()
6、Since the minimum voltage is 2.4 V when the 74TTL outputs high level and 3.5 V when the 74HCMOS inputs high level, TTL cannot directly drive CMOS. ()
Chapter 10 Designing Combinational Circuits and Sequential Circuits
Chapter Test
1、The basic component of a combinational logic circuit is: ().
A、Gate circuit
B、Flip-flop
C、Operational amplifier
D、Register and capacitor
2、When debugging a combinational logic circuit, the high and low levels shall satisfy: ().
A、High level > 3V, low level < 1V;
B、High level > 3V, low level < 0.4V;
C、High level > 4V, low level < 0.4V;
D、All of the above are acceptable.
3、Sequential logic circuit has an output signal that depends only on the current input signal and is independent of the state of the circuit. ()
4、The preset terminal and reset terminal of D flip-flop can be valid at the same time. ()
5、In sequential logic circuits, after the rising edge of the clock arrives, the input signal will remain stable for a period of time, which is called hold time. ()
6、Static debugging and dynamic debugging methods can be used to debug sequential logic circuits. ()
Chapter 11 Common-emitter (CE) Amplifier
Chapter Test
1、Negative half-cycle distortion occurs in the output waveform of the common-emitter amplifier because: ().![]()
A、The Quiescent point is low leading to cut-off distortion.
B、The Quiescent point is low leading to saturation distortion.
C、The Quiescent point is high leading to cut-off distortion.
D、The Quiescent point is high leading to saturation distortion.
2、The phase difference between the input voltage and the output voltage of the common-emitter amplifier is: ().
A、0°
B、45°
C、90°
D、180°
3、Which of the following feedback can increase the input resistance? ()
A、Voltage - parallel negative feedback
B、Voltage - series negative feedback
C、Current - parallel negative feedback
D、Current - series negative feedback
4、Which of the following feedback can reduce the output resistance? ()
A、Voltage - parallel negative feedback
B、Voltage - series negative feedback
C、Current - parallel negative feedback
D、Current - series negative feedback
5、The measurement of dynamic parameters of the amplifier must be carried out in the absence of distortion. If there is signal distortion, effort must be made to eliminate the distortion according to the specific situation of the distortion before performing dynamic parameter test. ()
6、For the common-emitter amplifier as shown in the figure, when the Quiescent point is low leading to cut-off distortion, the resistance value of potentiometer RW shall be reduced in order to eliminate the distortion. ()![]()
7、Negative feedback can increase the amplification of the amplifier. ()
Chapter 12 The Application of 555 Integrated Timer
Chapter Test
1、555 timer is a ().
A、Digital integrated circuit
B、Analog-digital hybrid integrated circuit
C、Analog integrated circuit
D、None of the above is true
2、The application of 555 timer does not include ().
A、Delay and timing
B、Signal amplification
C、Pulse shaping
D、Pulse generation
3、The waveform that a multivibrator composed of 555 timer can generate is ().
A、Sinusoidal Wave
B、Triangular wave
C、Irregular waveform
D、Rectangular wave
4、The width (T) of output pulse from a monostable flip-flop composed of 555 is ().![]()
A、T=1.3RACt
B、T=1.5 RACt
C、T=0.9 RACt
D、T=1.1 RACt
5、The maximum value of VC measured in the monostable flip-flop composed of 555 timer is: ().![]()
A、2/3VCC
B、1/2 VCC
C、VCC
D、1/3 VCC
6、Under the effect of the trigger signal from the monostable flip-flop the circuit turns over from the steady state to the transient stable state where it stays for some time, and then automatically returns to the steady state. ()
7、The high-level width and low-level width of the rectangular wave generated by a multivibrator composed of 555 timer are equal. ()
8、The comparison voltages of comparators C1 and C2 are 2/3VCC and 1/3VCC respectively only when Pin 5 of 555 timer is suspended, that is, when the applied control voltage is 0. ()
Chapter Test
1、The safety voltage for continuous contact with human body is not higher than () V, and the safety current is not higher than () mA.
A、12, 5
B、24, 10
C、36, 15
D、48, 20
2、In order to improve the effectiveness of classroom experiments, which of the following items shall be done: ()
A、Before the experiment, a measurement data sheet should be designed and the number and interval of measuring points reasonably selected. If the data to be measured is on the curved part of a curve, more measuring points should be arranged whereas fewer points are required on the smooth part. In this way, better results can be obtained from curve fitting in subsequent data processing.
B、Continuity test shall be conducted on the conductor before overlapping the circuit.
C、Usually, the "loop connection method" is adopted through sequential wiring from the power supply until the whole circuit is completed.
D、For a more complex circuit, it shall be divided into several independent sub-circuits according to its functions and completed step by step.
3、In the experiment class, which of the following measures shall be taken to protect against electric shock: ()
A、Do not place drinks, cups and other items on the experiment table.
B、Do not touch experiment devices, instruments and equipment with wet hands.
C、Connect the circuit on an insulation pad carefully according to the circuit diagram, and check it after it is connected. If necessary, ask the teacher to recheck it to ensure that it is correct before switching on the power supply. If it is necessary to change or disconnect the line during the experiment, cut off the power supply before performing any operation.
D、If any abnormal phenomena arise during the experiment such as heating, luminescence, sound and smell, cut off the power supply immediately, report to the teacher and identify the cause to prevent failure propagation.
4、In the experiment class, in case of an electric shock accident, which of the following measures shall be taken: ()
A、The first thing is to ensure the safety of the rescuers themselves.
B、Then disconnect the person who gets an electric shock from the power supply. The most effective way to do this is to directly close the switch and cut off the power supply.
C、Insulating objects such as dry wooden sticks shall be used to separate the electric shock victim from the power source.
D、Call the 120 first-aid phone number at once and adopt artificial respiration in case of emergency. Then call Beihang University Alarm Center at 82317119.
5、The main causes of electric fires include: ()
A、Electric leakage
B、Short circuit
C、Excess load
D、Excessive contact resistance
6、Which of the following shall be used for extinguishing electric fire: ()
A、Water
B、Carbon-dioxide (fire) extinguisher
C、Foam fire extinguisher
D、Powder fire extinguisher
Chapter 2 Common Instruments
Chapter Test
1、What factors shall be considered when selecting instruments? ()
A、Accuracy of instruments.
B、Impedance of instrument.
C、Frequency range of instrument.
D、All of the above shall be considered.
2、Which wiring method shall be selected to measure 10kΩ resistance using TH1941 digital multimeter? ()
A、
B、
C、
D、All of the above methods are OK.
3、Which system shall be adjusted to stably display the measured waveform on the oscilloscope? ()
A、Vertical system.
B、Horizontal system.
C、Triggering system.
D、All of the above shall be adjusted.
4、Which methods could be used for measuring signal amplitude with a digital oscilloscope? ()
A、Calculation of grid number.
B、CURSOR measurement method.
C、MEASURE measurement method.
D、All of the above methods are OK.
5、Using digital oscilloscope to observe the waveform of DC signal, which coupling method shall be selected for the measurement channel? ()
A、DC coupling.
B、AC coupling.
C、Grounding.
D、All of the above are acceptable.
6、Which two terminals shall be selected when MPS-3003LK-3 DC stabilized power supplies is used to output +12V? ()
A、1, 3
B、2, 3
C、4, 5
D、All of the above are acceptable.
7、The signal output of the function signal generator can be short circuited. ()
Chapter 3 Circuit Design and Simulation
Chapter Test
1、When using Proteus software to control the visual field of the editing area, press keys F5 (), F6 (), F7 (), F8 (). (1) Reduce. (2) Amplify. (3) Display the whole drawing. (4) Display a graph centered on the mouse pointer. The correct order should be: ()
A、(1), (2), (3), (4).
B、(4), (2), (1), (3).
C、(1), (3), (2), (4).
D、(4), (1), (2), (3).
2、When using an oscilloscope to observe signals, the trigger function plays an important role in stabilizing the signal waveform, and the trigger level shall generally be adjusted to: ()
A、The middle of the observation area.
B、The peak of the observation signal.
C、Within the amplitude range of the observed waveform.
D、The valley of the observation signal.
3、During the "common-emitter amplifier" simulation test, the Quiescent point can be adjusted by using: ()
A、Voltage probe
B、Current probe
C、AC voltmeter
D、DC voltmeter
4、When using Proteus software, it is necessary to check the electrical rules after connecting the circuit. ()
5、When using Proteus software, click "Run Simulator by Dynamic Frame" to facilitate single-step operation and observe the simulation process. ()
6、When using a probe to test current, it is required that the arrow of current probe be perpendicular to the conductor, otherwise an error will be reported. ()
7、During the "common-emitter amplifier" simulation test, dynamic parameters shall be measured while ensuring the output waveform is not distorted. ()
Chapter 4 Remote Online Circuit Experiment
Chapter Test
1、In the software interface of the remote online experiment platform, click "Scan" to display the modular components which have been furnished on the current experiment platform.
2、In the software interface of the remote online experiment platform, click "Find Instrument" to display the required instrument and equipment list, and this indicates that the instruments are successfully connected.
3、In the remote online experiment, the circuit is created. If there are key errors in the wiring, the system will check and find them so as to avoid issuing the circuit to cause damage.
4、In the remote online experiment, every time the circuit connection is modified, it is necessary to click "Issue" again and then click "Refresh Measurements" to ensure that the measurements are consistent with the actual situation.
5、In the software of the remote online experiment platform, check the required test items and click "Refresh Measurements" to update the results continuously.
6、In the software of the remote online experiment platform, "Waveform Screenshot" displays the test results of all test items on CH1 on the basis of recording two channel’s waveforms.
Chapter 5 Construction and Measurement of DC Circuit
Chapter Test
1、Which of the following are non-linear elements?
A、Resistance
B、Inductance with iron core
C、Field effect tube
D、Diode
2、The circuit "Ground” is signal "Ground", also known as the “Reference Ground", which is the zero-potential reference point. Which of the following signals should be connected to the "Ground" terminal when conducting the circuit "Common Ground” measurement?
A、Power supply ground
B、Black clamp of O-scope probe cable
C、Black clamp of signal generator probe cable
D、Amplifier circuit ground
E、Multimeter black test lead
3、In the circuit, the linear element's current is proportional to the voltage, the volt-ampere charac. curve is a straight line passing through the origin of coordinate, and Ohm's law applies to the linear element. Except for some ordinary resistors, the daily used components are basically linear components.
4、In this experiment, when testing the volt-ampere characteristics of voltage-adjustable signal source, by changing the load resistance to change the loop current, the corresponding output voltage can be measured, and then the internal resistance of the power supply can be calculated.
5、In this experiment, when testing the output characteristics of voltage-adjustable signal source, a fixed resistor is added to the bleeder circuit. According to the circuit’s needs, this resistor can be omitted in general.
6、In the experiment of the R/2R shunt circuit, the voltage division is achieved through branch shunt.
7、When measuring the current, it is necessary to connect an ammeter (or an multimeter in current mode) in series to the branch to be measured. In electronic circuits, indirect measurement is often used. By connecting a relatively small resistance in series to a branch, that is, to measure the voltage across a known resistance with a voltmeter, and then determine the current value.
8、For connection of experimental circuit, the loop method is often used, which generally starting from the positive pole of a power supply, and connect one loop after another. For the following R/2R shunt circuit, the circuit wiring sequence can be: 1-2-3-4，2-5-6-7-8-3，7-9-10-11-12-8，11-13-14-15-16-12，15-17-18-16
Chapter 6 Attenuator & RC Low-pass Filter
Chapter Test
1、For the low-pass filter as shown in the figure, the corner frequency is:
A、
B、
C、
D、
2、As shown in the figure, connect an attenuator between the signal source and the load RL. At this point, the power obtained by the load is 1% of that when the signal source and the load are directly connected, then the relationship between U1 and U2 should be:
A、U1 =2U2
B、U1 =5U2
C、U1 =10U2
D、U1 =100U2
3、Which of the following description of measuring frequency characteristics by the dot frequency measurement method is incorrect?
A、In the process of measurement, attention should be paid to the output signal to ensure no distortion.
B、Near the corner point, the measurement frequency points should be denser.
C、Select the test frequency points uniformly in the frequency range.
D、The abscissa of amplitude-frequency curve generally adopts logarithmic coordinate, and the test frequency is selected according to logarithmic law.
4、Frequency characteristic measurement includes amplitude-frequency and phase-frequency characteristic measurements.
5、A filter is used to intercept the signal according to the required frequency band, including high-pass filter, low-pass filter, band-pass filter, band-elimination filter and so on.
6、Any passive linear two-port network can be equivalent to a two-port network composed of three impedances.
Chapter 7 Coil Parameter Measurement and Three-phase Circuit
Chapter Test
1、After connecting a capacitor in parallel at both ends of the inductive load, the circuit’s average power:
A、Increases
B、Decreases
C、Remains unchanged
D、Is unknown
2、In the three-phase circuit, which of the following description of the neutral line is incorrect?
A、The neutral line can make each phase independent, and the work of each phase does not affect each other.
B、In the case of asymmetric load, the neutral line can play a role in ensuring safe power supply.
C、In a symmetrical three-phase circuit, the neutral line current is 0.
D、In an asymmetrical three-phase circuit, the neutral line current is 0.
3、The inductance of both air-core and iron-core coil are constant at low frequencies.
4、Connecting a capacitor in parallel at both ends of the inductive load can improve the power factor.
5、In the experiment, when the power is turned on and off, the measuring instrument should not be connected to the circuit.
6、Connecting a capacitor in parallel at both ends of the inductive load can improve the power factor, and the larger the capacitance is, the larger the power factor will be.
Chapter 8 A Circuit’s Frequency Characteristics and Square Wave Response
Chapter Test
1、Regarding the oscilloscope, which of the following statements is correct?
A、An oscilloscope can only be used to observe the waveform of voltage signal
B、There are only two measurement methods for digital oscilloscope waveform parameters: counting of grid number and cursor-assisted measurement method
C、An oscilloscope can be used to directly observe the waveform of current
D、An oscilloscope usually has 2 working modes: Y-T and X-Y modes
2、After turning on the O-scope’s power, the reason that the scan line does not appear on the screen at the beginning may be:
A、The horizontal or vertical displacement of CH1 or CH2 is incorrect ("beyond" the screen)
B、The screen brightness is adjusted too dark
C、The trigger source is incorrectly selected
D、The X-Y mode is used
3、The reason that a scope-displayed waveform is unstable may be:
A、The trigger source is incorrectly selected
B、The Sensitivity knob is improperly adjusted
C、The X-Y mode is used
D、The trigger level is not adjusted well
4、Use an oscilloscope to simultaneously observe two signals of different frequencies. By which of the following methods are the waveform generally easy to adjust and stabilize?
A、Use the channel with the high frequency signal as the trigger source
B、Use the channel with the low frequency signal as the trigger source
C、Adjust the trigger level line to fall within the range of low-freq. signal waveform
D、Adjust the trigger level line to fall within the range of high-freq. signal waveform
5、What issues should be attended to when two channels of an oscilloscope are being used?
A、Any position can be arbitrarily observed on two channels, by the same method as one channel is used alone.
B、When two channels of an oscilloscope are simultaneously used, the two black clamps should be connected together, or only one of them should be used and the other dangling.
C、When two channels of an oscilloscope are simultaneously used, the two black clamps should be connected together before connecting to the circuit “Ground”.
D、When two channels of an oscilloscope are simultaneously used to observe the circuit waveforms, there should be no components connected between the two black clamps.
Chapter 9 TTL and CMOS Gate Circuits
Chapter Test
1、In TTL and CMOS interconnection experiments, based on oscilloscope waveforms the TTL rise rate can be calculated as (), and CMOS rise rate as (). ()
A、32ns, 118ns
B、131.25V/us, 27.1V/us
C、118ns, 32ns
D、27.1 V/us, 131.25 V/us
2、When testing the voltage transmission characteristics of TTL NAND gate (74LS00), the input signal is 500Hz (), and () mode shall be selected when observing the oscilloscope waveform. ()
A、Sinusoidal Wave, Y-T.
B、Sawtooth wave, X-Y.
C、Sinusoidal Wave, X-Y.
D、Sawtooth wave, Y-T.
3、TTL NAND gate opening level UON refers to the input level when the output level has just dropped to the upper limit of the output low level. It is the maximum input high level value allowed to ensure the output of NAND gate is low level (); the closing level UOFF refers to the input level when the output level has just risen to the lower limit of the output high level. It is the minimum input low level value allowed to ensure the output of NAND gate is high level. ()
4、The redundant or temporarily unused input terminals of TTL circuit cannot be suspended. For TTL NAND gate, the unused input terminals can be connected in parallel or directly to high level. For TTL NOR gate, unused input terminals can be connected in parallel or directly to low level. ()
5、CMOS chips generally have a protecting circuit inside. In order for the protecting circuit to work, the chip power supply shall be switched on before adding an external signal source. After completion, the signal source shall be switched off before the power supply is turned off. ()
6、Since the minimum voltage is 2.4 V when the 74TTL outputs high level and 3.5 V when the 74HCMOS inputs high level, TTL cannot directly drive CMOS. ()
Chapter 10 Designing Combinational Circuits and Sequential Circuits
Chapter Test
1、The basic component of a combinational logic circuit is: ().
A、Gate circuit
B、Flip-flop
C、Operational amplifier
D、Register and capacitor
2、When debugging a combinational logic circuit, the high and low levels shall satisfy: ().
A、High level > 3V, low level < 1V;
B、High level > 3V, low level < 0.4V;
C、High level > 4V, low level < 0.4V;
D、All of the above are acceptable.
3、Sequential logic circuit has an output signal that depends only on the current input signal and is independent of the state of the circuit. ()
4、The preset terminal and reset terminal of D flip-flop can be valid at the same time. ()
5、In sequential logic circuits, after the rising edge of the clock arrives, the input signal will remain stable for a period of time, which is called hold time. ()
6、Static debugging and dynamic debugging methods can be used to debug sequential logic circuits. ()
Chapter 11 Common-emitter (CE) Amplifier
Chapter Test
1、Negative half-cycle distortion occurs in the output waveform of the common-emitter amplifier because: ().
A、The Quiescent point is low leading to cut-off distortion.
B、The Quiescent point is low leading to saturation distortion.
C、The Quiescent point is high leading to cut-off distortion.
D、The Quiescent point is high leading to saturation distortion.
2、The phase difference between the input voltage and the output voltage of the common-emitter amplifier is: ().
A、0°
B、45°
C、90°
D、180°
3、Which of the following feedback can increase the input resistance? ()
A、Voltage - parallel negative feedback
B、Voltage - series negative feedback
C、Current - parallel negative feedback
D、Current - series negative feedback
4、Which of the following feedback can reduce the output resistance? ()
A、Voltage - parallel negative feedback
B、Voltage - series negative feedback
C、Current - parallel negative feedback
D、Current - series negative feedback
5、The measurement of dynamic parameters of the amplifier must be carried out in the absence of distortion. If there is signal distortion, effort must be made to eliminate the distortion according to the specific situation of the distortion before performing dynamic parameter test. ()
6、For the common-emitter amplifier as shown in the figure, when the Quiescent point is low leading to cut-off distortion, the resistance value of potentiometer RW shall be reduced in order to eliminate the distortion. ()
7、Negative feedback can increase the amplification of the amplifier. ()
Chapter 12 The Application of 555 Integrated Timer
Chapter Test
1、555 timer is a ().
A、Digital integrated circuit
B、Analog-digital hybrid integrated circuit
C、Analog integrated circuit
D、None of the above is true
2、The application of 555 timer does not include ().
A、Delay and timing
B、Signal amplification
C、Pulse shaping
D、Pulse generation
3、The waveform that a multivibrator composed of 555 timer can generate is ().
A、Sinusoidal Wave
B、Triangular wave
C、Irregular waveform
D、Rectangular wave
4、The width (T) of output pulse from a monostable flip-flop composed of 555 is ().
A、T=1.3RACt
B、T=1.5 RACt
C、T=0.9 RACt
D、T=1.1 RACt
5、The maximum value of VC measured in the monostable flip-flop composed of 555 timer is: ().
A、2/3VCC
B、1/2 VCC
C、VCC
D、1/3 VCC
6、Under the effect of the trigger signal from the monostable flip-flop the circuit turns over from the steady state to the transient stable state where it stays for some time, and then automatically returns to the steady state. ()
7、The high-level width and low-level width of the rectangular wave generated by a multivibrator composed of 555 timer are equal. ()
8、The comparison voltages of comparators C1 and C2 are 2/3VCC and 1/3VCC respectively only when Pin 5 of 555 timer is suspended, that is, when the applied control voltage is 0. ()