Power Electronics MCQ Questions and Answers for Practice

1. 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

2. A diac has........................terminals

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

3. A diac has....................pn junctions

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

4. A diac has ................... semiconductor layers

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

5. 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

6. A diac is turned on by ...................

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

7. A full wave rectifier with resistive load produces

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

8. A triac can pass a portion of ..................... half-cycle through the load

1. Only negative
2. Both positive and negative
3. Only positive
4. None of the above

9. A triac has .................... semiconductor layers

1. Three
2. Four
3. Two
4. Five

10. A Triac has three terminals viz.....................

1. Two main terminal and a gate terminal
2. Cathode, anode, gate
3. Drain, source, gate
4. None of the above

11. A triac is a ................ switch

1. Unidirectional
2. Mechanical
3. Bidirectional
4. None of the above

12. A triac is equivalent to two SCRs .......................

1. In series
2. In inverse-parallel
3. In parallel
4. None of the above

13. A UJT has ....................

1. One pn junction
2. Three pn junctions
3. Two pn junctions
4. None of the above

14. A UJT is sometimes called................ diode

1. High resistance
2. Single-base
3. Low resistance
4. Double-base

15. AC power in a load can be controlled by using

1. two SCRs in series
2. three SCRs in series
3. two SCRs in parallel opposition
4. four SCRs in series