所屬科目：中山◆電機◆電磁學
1. A Lithium Ion battery module is rated at 12V/6Ah. Two modules in series connection are discharged by 0.5C constant current for 0.5 hour. Determine the total energy supplied by batteries.(A)144Whr(B)72Whr(C)36Whr(D)18Whr
2. Current 2mA flows into two resistors 10kΩ in parallel connection. Determine power consumption for each resistor.(A)80mW(B)40mW(C)20mW(D)10mW
3. DC voltage source 10 V is applied to a series RL circuit with parameters L=4H, R=10Ω. Choose a false statement.(A)Inductor current is 1A(B)Inductor voltage is 10V(C)Resistor current is 1 A(D)Resistor voltage is 10V
4. Determine impedance of a series RLC circuit with L=2H, C=1F, R=1Ω at w=1rad/s.(A)1-jΩ(B)1+jΩ(C)1-0.5jΩ(D)1+0.5jΩ
5. Determine the cut-off frequency of a series RC low-pass filter with parameters C=0. 5F and R=4Ω.(A)0.5 rad/s(B)1 rad/s(C)2 rad/s(D)4 rad/s
6. Determine RMS current of a load (impedance 10+j10Ω) if applied RMS voltage 141V.(A)20A(B)14A(C)10A(D)0.7A
7. AC voltage 141 cos(377t) V is applied on a resistor R=10Ω. Determine its average power.(A)1000W(B)500W(C)250W(D)0W
8. AC voltage source 100cos(377t) V is applied to an inductor (100mH). Choose a false statement.(A) instantaneous power is equal to average power(B) reactive power is equal to apparent power(C) power factor is equal to 0(D) average power is equal to 0
9. For an AC circuit, choose a false statement.(A) an inductor consumes reactive power(B) a capacitor supplies reactive power(C) average power of an inductor is zero(D) apparent power of an inductor is zero
10. A delta-connected resistive load 100Ω per phase is connected to a balanced three-phase three-wire 200V circuit. Choose a false statement.(A) power factor is 1(B) reactive power is 0(C) average power is 1200W(D) line current is 2A
11. A Y-connected resistive load 20Ω per phase is connected to a balanced three-phase four-wire voltage source. Line voltage is 173V. A neutral line with resistance 10Ω is connected between source and load. Choose a false statement.(A) Load current is 5A(B) Line current is 8.65A(C) Neutral current is 0A(D) Total power is 1500W
12. For an ideal transformer, voltage at the primary side and the secondary side are 500V and 100V, respectively. Secondary side is connected to a 100Ω resistor. Choose a false statement.(A) output power is 100W(B) input power is 100W(C) output current is 1A(D) input current is 1A
13. Determine average dc output voltage of a half-wave rectifier applied by 100V RMS ac voltage.(A) 141.4V(B) 100V(C) 70.7V(D) 45V
14. Current is equal to 10+10 cos(377t)+10 cos(1131t) A. Determine its RMS value.(A) 28.28A(B) 20A(C) 14.14A(D)10A
15. An ideal buck converter is operated in CCM mode. Input voltage is 20V, output voltage is 10V and load resistance is 2Ω. Choose a false statement.(A) Average input current is 2.5A(B) Average output current is 5A(C) Average inductor voltage is 10V(D) Average diode voltage is 10V
16. An ideal boost converter is operated in CCM mode. Input voltage is 10V and output voltage is 50V and load resistance is 10Ω. Choose a false statement.(A) Average inductor current 5A(B) Duty ratio is 0.8(C) Input power is 250W(D) Output power is 250W
17. An ideal boost-boost converter is operated in CCM mode. Input voltage is 10V and output voltage is 20V and load resistance is 10Ω. Choose a false statement.(A) Duty ratio is 0.67(B) Average inductor current is 8A(C) Input current is 4A(D) Output current 2A
18. Determine the speed of rotation of a synchronous generator with parameters 480V/50Hz/six poles/delta-connection.(A) 600rpm(B) 1000rpm(C) 1200rpm(D) 2000rpm
19. A four-pole, 60Hz induction motor supplies 15kW to a load at 5% slip. Choose a false statement.(A) Synchronous speed is 1800 rpm(B) Rotor speed is 1710 rpm(C) Rotor frequency is 3Hz(D) Load torque is 41.7N·m
20. A single-phase transformer is rated at 220/440V, 10kVA. Leakage reactance measured from the low-voltage side is 0.24Ω. Choose a false statement.(A) Base impedance at the low-voltage side is 4.84Ω(B) Base impedance at the high-voltage side is 19.36Ω(C) Leakage reactance at the low-voltage side is 0.050 pu(D) Leakage reactance at the high-voltage side is 0.012 pu
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