Power Electronics Multiple Choice Questions and Answers

11. A triac has .................... semiconductor layers

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

12. 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

13. A triac is a ................ switch

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

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

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

15. A UJT has ....................

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

16. A UJT is sometimes called................ diode

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

17. 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

18. After peak point, the UJT operates in the ................... region

1. Saturation
2. Negative resistance
3. Cut-off
4. None of the above

19. An SCR can be used

1. for power control
2. for speed control of dc shunt motor
3. as static conductor
4. all of these

20. An SCR is made up of silicon because

1. silicon has small leakage current than germanium
2. silicon has small leakage voltage than germanium
3. silicon has large leakage current than germanium
4. silicon has large leakage voltage than germanium