Power Electronics Objective Questions | MCQ Quiz for Practice

61. Voltage commutation circuit can be converted into a current commutation by interchanging the positions of

1. Capacitor and SCR
2. Inductor and capacitor
3. Diode and capacitor
4. Capacitor and load

62. When a UJT is turned ON, the resistance between emitter terminal and lower base terminal.................................

1. Is decreased
2. Is increased
3. Remains the same
4. None of the above

63. When the emitter terminal of a UJT is open, the resistance between the base terminal is generally .......................

1. Low
2. Extremely low
3. High
4. None of the above

64. When the temperature increases, the inter-base resistance (RBB) of a UJT ......................

1. Decreases
2. Remains the same
3. Increases
4. None of the above

65. When the temperature increases, the intrinsic stand off ratio ....................

1. Decreases
2. Essentially remains the same
3. Increases
4. None of the above

66. Which of the following is not a characteristic of UJT?

1. Negative resistance
2. Peak-point voltage
3. Intrinsic stand off ratio
4. Bilateral conduction

67. With increase in firing angle

1. Harmonic distortion increases and quality of input current decreases
2. Harmonic distortion decreases and quality of input current increases
3. Both harmonic distortion and quality of input current increases
4. Both harmonic distortion and quality of input current decreases

68. A crowbar is a circuit which is used to protect a

1. current sensitive load from excessive dc power supply output voltages
2. voltage sensitive load from excessive ac power supply output voltages
3. voltage sensitive load from excessive dc power supply output voltages
4. current sensitive load from excessive ac power supply output voltages

69. A diac has ................... terminals

1. Three
2. Four
3. Two
4. None of the above

70. A diac has …………… pn junctions

1. Two
2. Three
3. Four
4. None of the above

71. A diac has ……………… semiconductor layers

1. Two
2. Four
3. Three
4. None of the above

72. A diac is …………………. switch

1. A d.c.
2. A mechanical
3. An c.
4. None of the above

73. A diac is simply ………………

1. A three junction device
2. A triac without gate terminal
3. A single junction device
4. None of the above

74. A diac is turned on by …………………

1. Gate voltage
2. Gate current
3. A breakover voltage
4. None of the above

75. A full wave rectifier with resistive load produces

1. Third harmonic
2. Fifth harmonic
3. Second harmonic
4. Do not produce harmonics