First, single-choice questions:
1. The resistance value of the metal conductor increases with temperature ( ). A: increase B: decrease C: constant D: weaken
2. The inductive reactance of a purely inductive circuit is ( ). A: LB: ωL C: 1 / ωL D: 1/2πfL
3. In the sinusoidal AC resistance circuit, the relationship between the current and voltage is correctly reflected as ( ). A: i=U/RB: i=Um/RC: I=U/RD: I=Um/R
4. In some cases, in order to shorten the on-time of the thyristor, increase the trigger current (more than twice). This current is called ( ). A: Trigger current B: Strong trigger current C: Clamp current D: On current
5. The three-phase load is connected to the three-phase power supply. If the rated voltage of each phase load is equal to the power line voltage 1 /, it should be connected. A: star B: triangle C: open triangle D: double star
6. The expression for active power in a single-phase sinusoidal AC circuit is ( ). A: UI B: UI C: UIcosφ D: UIsinφ
7. The phase relationship between current and voltage in a pure capacitor AC circuit is current ( ). A: Leading 90° B: Hysteresis 90° C: In-phase D: Leading 0~90°
8. The two sine quantities are u1=36sin(314t+120°)V, u2=36sin(628t+30°)V, then there is ( ). A: u1 leads u290° B: u2 is 90° ahead of u1 C: Cannot judge phase difference D:
9. The output impedance of the emitter output ( ) is commonly used at the output pole. A: Higher B: Low C: Not high or low D: Very high
10. When the diode is half-wave rectified, the DC voltage across the load is equal to ( ). A: 0.75U2 B: U2 C: 0.45U2 D: 0.9U2
11. The connection group of the three-phase transformer is indicated by ( ). A: Phase relationship of the original pay side voltage B: The same name end relationship of the original pay side C: Time-to-center relationship of the original pay side voltage D: The relationship between the original pay side current and the magnitude
12. The voltage amplification of the emitter output is approximately equal to ( ). A: 80--100 B: 1 C: <50
13. The larger the control angle of the thyristor, the output voltage ( ). A: Higher B: shift phase C: lower D: bigger
14. In the initial phase angle of a sinusoidal AC voltage, φU = π / 6, and at t = 0, its instantaneous value will be ( ). A: less than zero B: greater than zero C: equal to zero D: indefinite
15. It is known that the time when msinwt reaches the maximum value for the first time is 0.005 s, and the time when the second time reaches the maximum value is ( ). A: 0.01s B: 0.025s C: 0.05s D: 0.075s
16. U = 311 sin (314 t - 15 °) volts, then U = ( ) volts. A: 220∠-195° B: 220∠1950° C: 311∠-15° D: 220∠-15°
17. The equivalent exchange between the actual voltage source and the actual current source is ( ) for the internal circuit. A: Can be equivalent B: Not equivalent C: Equivalent when the circuit is linear D: Equivalent when the circuit is nonlinear
19. Any condition can be affirmed, this is () logic.
A: with B: or C: or non-D: non
20. In the amplifying circuit, in order to stabilize the output current, ( ) should be introduced.
A: Voltage negative feedback B: Positive voltage feedback C: Current negative feedback D: Positive current feedback
twenty one. Z=A+B is the () logic.
A: and B: with or not C: with or not D: or not
twenty two. In the triode amplifier circuit, the amplifier circuit should be used to enhance the load capacity.
A: common emitter B: common base C: common collector D: common cathode
twenty three. The logic against which the conclusion is opposite to the given condition is ( ).
A: and B: or C: and non-D: non
twenty four. It is known that the potential of three pins in the amplifying circuit to ground is (1) 0V; (2) 0.7V; (3) 6V, the triode is of type ( ).
A: NPN B: PNP C: Silicon tube D: tube
25. The amplifier uses emitter bias to improve the operating point deviation ( ).
A: Current positive feedback B: Current negative feedback C: Positive voltage feedback D: Voltage negative feedback
26. The positive blocking of the thyristor is ( ).
A: thyristor plus small anode voltage, control pole plus reverse voltage B: controllable earth plus factory to anode voltage, control pole without reverse voltage
C: thyristor plus reverse anode voltage, control pole plus forward voltage D: thyristor plus reverse anode voltage, control pole plus reverse voltage
27. A three-phase symmetrical load, delta connection, is known: phase current IBC = 10 ∠-10 ° ampere, then line current I = ( ) ampere.
A: 17.3∠-40° B: 10∠-160° C: 10∠80° D: 17.3∠80°
28. The single-phase half-wave thyristor rectifier circuit determines the component of the control angle ( ).
A: U2 B: U2/2 C: U2 0.45U2
29. All conditions are in place, and there is a definite conclusion. This is () logic.
A: and non-B: or non-C: and D: non
30. Single-phase bridge type semi-controlled rectifier circuit, by changing the control angle, the load voltage can be continuously adjusted between ( ).
A: 0~0.45U2 B: 0~0.9U2 C: 0~U2 D: 0~2.34U2
31. It is known that I = -14.1 sin 100 πtA, and its current phasor I = ( ) A.
A: 14.1∠0° B: 14.1∠180° C: 10∠0° D: 10∠-180°
32. The thyristor conduction condition is ( ).
A: anode and cathode plus forward voltage, control pole and anode plus reverse voltage B: anode and cathode plus forward voltage, control pole and cathode plus forward voltage
C: Reverse voltage is applied to the anode and cathode, and reverse voltage is applied to the control electrode and the anode. D: Reverse voltage is applied to the anode and anode, and forward voltage is applied to the control electrode and the cathode.
33. The transistor's emitter junction is reverse biased, the collector junction is biased, and the transistor is in ( ) operation.
A: Zoom B: Cutoff C: Saturated D: Open circuit
34. The emitter junction of the transistor is positively biased, and the collector junction is reverse biased, and the working state of the transistor is ( ).
A: Saturated B: Cutoff C: Zoom D: Conduction
35. It is known that e = 311 sin (314t + 5 °) V, and its phasor E = ( ).
A: 311 ∠5 ° B: 220 ∠5 ° C: 220 ∠+ 185 ° D: 220 ∠+ 175 °
36. The Thevenin's theorem applies only to ( ).
A: The external is a nonlinear circuit B: the external is a linear circuit C: the internal is a linear source circuit D: the internal circuit is a nonlinear source circuit
37. The thyristor has a ( ) PN junction.
A: 1 B: 2 C: 3 D: 4
38. The current of the capacitor I = C ΔUC / Δt, when UC increases, the capacitor is ( ).
A: Charging process and drawing electric energy into electric field energy B: charging process and drawing electric field energy into electric energy
C: discharge process and released by electric field energy into electric energy D: discharge process and release of electric energy into electric field energy
39. The transistor is in an amplified state, and the collector potential is 6V, the base potential is 0.7V, and the emitter is grounded. The transistor is ( ).
A: NPN B: PNP C: ND: P
40. It is known that the current I=6+j8, the power frequency is 50Hz, and the instantaneous value expression is I=().
A: 10 sin (314t+53.1°) B: 10 sin (314t+36.9°)
C: 10sin (314t+53.1°) D: 10sin (314t+36.9°)
41. For a common emitter amplifier, the collector resistor RC acts as ( ).
A: Realize current amplification B: Transistor current amplification to convert the transmission into voltage amplification C: Current amplification and voltage amplification D: Stable operating point
42. The three-phase power supply Y is connected, and it is known that UB = 220 ∠-10 ° volts, and its UAB = ( ) volt.
A: 220∠20° B: 220∠140° C:380∠140° D:380∠20°
43. The initial phase angle of a sinusoidal AC voltage is φ=-π/6, and at t=0, its instantaneous value will be ( ).
A: greater than zero B: less than zero C: equal to zero D: maximum
44. The condition under which LC series resonance occurs is ( ).
A: ωL=ωC B: L=CC: ωL=1/ωC D: XL=2πfL
45. If the voltage across a component in the circuit is u=100 sin (100πt+50°)V, current I=10 sin (100πt+140°)A, then the component is ( ).
A: Resistor B: Inductance C: Capacitor D: Resistor
46. The phase relationship between current and voltage in the RC circuit is the current ( ) voltage.
A: Leading 90° B: Hysteresis 90° C: In-phase D: Leading 0~90°
Second, multiple choice questions:
1. In a sinusoidal AC circuit, the following formula is correct ( ).
A:ic=duc/dt B:Ic=jwcU C:UC=-jwct D:XC=1/wc E:QC=UIsinφ
2. There are three basic logic circuits, namely ( ).
A: NAND gate B: AND gate C: NOT gate D: NOR gate E: OR gate
3. For a three-phase symmetrical AC circuit, regardless of the star or delta connection, the following conclusions are correct ( ).
A: P = 3UmImcosφ B: S = 3UmIm C: Q = U1I1sinφ D: S = E: S = 3UI
4. The multi-stage amplifier pole coupling form is ( ).
A: Diode B: Resistor C: Resistor D: Transformer E: Direct
5. The most basic logic circuit of an electronic circuit is ( ).
A: AND gate B: NOT gate C: AND NOT D: OR gate E: XOR
6. Kirchhoff's law has ( ).
A: node current law B: loop voltage law C: circuit current law D: node voltage law
7. The three elements of sinusoidal alternating current are ( ).
A: Maximum value B: Initial phase angle C: Angular frequency D: Series E: Parallel
8. China has specified the connection group of three-phase power transformers ( ) and so on.
A: Y/Δ-11 B: Y0/Δ-11 C: Y0/Y-12D: Y/Y-12 E: Y/Δ-7
9. The method of artificially increasing the power factor is ( ).
A: Parallel appropriate capacitor B: circuit in series with appropriate capacitor C: parallel large reactor D: series large capacitor E: series appropriate inductance
10. The three-phase load symmetry is ( ).
A: The impedance values ​​of the phases are equal. B: The impedance difference of each phase C: The phase complex angles of each phase are 120° D. The phase angles of the impedances are equal. E: The phase complex angles of the phases are 180°.
11. The thyristor conduction condition is ( ).
A: A forward voltage is applied between the anode and the cathode. B: A reverse voltage is applied between the anode and the cathode.
C: a forward voltage is applied between the control electrode and the cathode. D: a reverse voltage is applied between the control electrode and the cathode. E: a forward voltage is applied between the anode and the control electrode.
12. Sinusoidal AC circuits, which of the following equations are correct? ( )
A: IL=U/XL B篣C=Xcic C:U=Ri D:X=X1+X2+X3 E:Z=Z1+Z2+Z3
13. The phasor of alternating current indicates that there are several forms of the symbol method? ( )
A: Algebraic B: Trigonometric C: Geometric D: Exponential E: Polar Coordinate
14. The benefits of improving the power factor are ( ).
A: You can make full use of the power supply equipment capacity B: can improve the output of the motor C: can reduce the line power loss
D: can reduce the starting current of the motor E: can increase the motor power
15. If the external power supply of the bridge is too high or too low, the phenomenon will occur.
A: Damage resistance B: Reduce sensitivity C: Reduce accuracy D: Cannot adjust to zero E: The reading is not allowed
16. The method of turning off the thyristor is ( ).
A: cut off the control electrode voltage B: disconnect the anode power supply C: reduce the forward anode voltage D: add the reverse voltage to the anode E: reduce the control pole current
17. When the three power supplies are connected to Y, the line voltage is ( ) times the phase voltage, and the line voltage leads the phase voltage ( ).
A: B: C: 60° D: 30° E: 90°
18. A three-phase symmetric inductive load, connected to the same power supply by triangle and Y, respectively, has the following conclusions: ( )
A: Load phase voltage: UΔ phase = 3UY phase B: Line current: IΔ phase = 3IY C: Power: PΔ = 3PY D: Phase current: IIΔ phase = IY E: The same phase voltage is tolerated
19. In the power system, the main function of reactive compensation using parallel compensation capacitors is ( ).
A: Improve power factor B: Improve equipment output C: Reduce power loss and power loss D: Improve voltage quality E: Improve lightning protection performance of overhead lines
20. In a sinusoidal AC circuit in series with RLC, when XL = XC, the circuit resonates and the resonance characteristic is ( ).
A: The voltage on the capacitor is equal to the voltage on the inductor, and the direction is opposite. B: The current in the circuit is the largest. C: The impedance in the circuit is the smallest.
D: The reactive power in the circuit is 0. E: The voltage on the resistor is equal to the applied voltage, and the direction is opposite.
twenty one. The measurement method of the single-phase transformer connection group is ( ).
A: DC method B: Resistance method C: AC method D: Power measurement method E: AC current method
twenty two. The Thevenin's theorem applies to external circuits as ( ) circuits.
A: Linear B: Rectifier C: Amplification D: Nonlinear E: Saturated
twenty three. It is known that the three-pin three-pin ground potential in the amplifying circuit is (1) 0V, (2) 0.7V, and (3) 6V. The electric field corresponding to each of the three poles is ( ).
A: (1) is the base B: (2) is the base C: (1) is the emitter D: (3) is the collector E: (3) is the emitter
twenty four. The limit parameters of the triode are mainly ( ).
A: Collector maximum allowable current ICM B: Set-emitter breakdown voltage (base open) UCEO C: Collector - base reverse saturation current ICBO
D: penetration current ICEO E: collector maximum allowable power dissipation PCN
25. The three configurations of the amplifier circuit are ( ).
A: Common emitter amplification B: Common collector amplification C: Saturated D: Cutoff E: Common base amplification
26. Let ia=Imsinωt of the three-phase sinusoidal alternating current, then ib is ( ).
A: ib=Imsin (ωt -120°) B: ib=Imsin (ωt +240°)
C: ib = Imsin (ωt - 240°) D: ib = Imsin (ωt + 120°) E: ib = Imsin (ωt ± 0°)
27. The three working states of the triode are ( ).
A: Open circuit B: Amplification C: Cutoff D: Short circuit E: Saturated
28. The blocking effect of the thyristor is ( ).
A: forward blocking B: reverse blocking C: forward bias D: reverse bias E: gate offset
29. The significance of improving the power factor is ( ).
A: Make full use of equipment capacity B: Improve power supply quality C: Reduce line power and voltage loss D: Save economic expenses E: Save line investment
30. The three configurations of the amplifier circuit are ( ).
A: Low frequency amplifier B: Common collector amplifier C: Common base amplifier D: Multipole amplifier E: Common emitter amplifier
Third, the judgment question:
1. The power factor is the difference between the phase of the voltage U and the current I in the load circuit. The larger the power factor, the smaller the power factor ( )
2. The full name of TTL integrated circuits is a transistor-transistor logic integrated circuit. ( )
3. When the emitter junction and collector junction of the triode are in a positively biased state, the triode must work in the saturation region ( )
4. In order to eliminate the effects of humidity changes, a crystal triode amplifier generally uses a fixed bias circuit. ( )
5. In the thyristor rectifier circuit, there is a certain energy requirement for the trigger pulse. If the pulse current is too small, the thyristor cannot be turned on. ( )
6. The difference in phase between the sinusoids of two different frequencies is called the phase difference ( )
7. Parallel capacitors increase the power factor of the inductive load itself. ( )
8. The superposition principle can only calculate the voltage and current with severe cold, and cannot be used to calculate the power of the circuit ( )
9. The larger the thyristor control angle, the higher the voltage. ( )
10. The phase of the AC voltage across an electrical component leads the current flowing through it, then the component is a capacitive load ( )
11. The conduction condition of the thyristor is the thyristor plus the forward voltage gate plus the reverse voltage. ( )
12. The thyristor has a positive and negative blocking capability. ( )
13. The inductive component does not consume energy in the circuit, it is a reactive load. ( )
14. The so-called partial circuit Ohm's law, part of the circuit refers to the circuit without power supply ()
15. The induced potential generated by the magnetic flux in the coil is proportional to the magnetic flux. ( )
16. The emitter output can be used not only as a voltage amplifier, but also to increase the input impedance and reduce the output impedance. ( )
17. The pulse front of the thyristor trigger circuit is steep and the leading edge rise time does not exceed 100μs. ( )
18. A single junction transistor has an emitter, a base, and a collector. ( )
19. When the emitter voltage of the single junction transistor is higher than the valley voltage, the transistor is turned on. ( )
20. The pure inductive load has a power factor of zero and the pure capacitive load has a power factor of 1.
Training answer
First, single-choice questions:
1 A 2 B 3 C 4 B 5 A 6 C 7 A 8 C 9 B 10 C 11 A 12 B 13C 14 B 15 B 16 D 17 B 18 C 19 B 20 C
21 D 22 C 23 D 24 A 25 B 26 B 27 D 28 29 C 30 B 31 D 32 B 33 B 34 C 35 D 36 C 37 C 38 A 39 A 40 A
41 B 42 C 43 B 44 C 45 C 46 D
Second, multiple choice questions:
1 BDE 2 BCE 3 ABCD 4 CDE 5 ABD 6 AB 7 ABC 8 ABCD 9 AB 10AD
11 AC 12 ACDE 13 ABCDE 14 AC 15 ABC 16 BCD 17 AD 18 BCD 19 ABCD 20 ABCD
21 AC 22 AD 23 BCD 24 ABCE 25 ABD 26 AB 27 BCE 28 AB 29 AC 30 BCE
Third, the judgment question:
1√ 2√ 3√ 4× 5√ 6× 7× 8√ 9× 10× 11× 12√ 13√ 14√ 15√ 16× 17× 18× 19× 20×
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