First, single-choice questions: 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 half Control the 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 of type (). 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° 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 Insulated Terminals,Terminals,High-quality insulated terminals Taixing Longyi Terminals Co.,Ltd. , https://www.longyicopperlugs.com
1. The resistance value of the metal conductor increases with temperature ( ). A: increase B: decrease C: constant D: weaken
December 08, 2022