Saturday 28 April 2012

Power Electronics

Q-1 What is the dominant form of distortion produced by the simple push-pull amplifier shown here?
ch09q01.gif

a) Harmonic distortion.
b) Clipping.
c) Crossover distortion.




Correct Answer:Crossover distortion.




Q-2 The efficiency of an electronic amplifier is important primarily because this determines the amount of waist heat produced within the amplifier.

a) True
b) False



Correct Answer:True


Q-3 What class of amplifier is shown here?

ch09q03.gif

a) Class A.
b) Class B.
c) Class AB.
d) Class C.


Correct Answer:Class A.


Q-4 In Class C amplifiers, the active devices are switches and are either completely ON or completely OFF.


a) True
b) False


Correct Answer:False


Q-5 The symbol for which component is shown here?


ch09q05.gif


a) A triac.
b) A thyristor.
c) A power diode.
d) A diac.


Correct Answer:A thyristor


Q-6 When a thyristor has been fired by an appropriate gate pulse, when will it to turn off?


a) After a fixed period of time determined by circuit components.
b) When a gate pulse of the opposite polarity is applied.
c) When the applied voltage changes polarity.
d) When the current through the device falls below the holding current.



Correct Answer: When the current through the device falls below the holding current.


Q-7 In the simple lamp dimmer shown here, what method of power control is being used?
ch09q07.gif


a) Proportional control.
b) Phase control.
c) Burst firing.
d) Feedback control.


Correct Answer:Phase control.


Q-8 Determine the output voltage of the following regulator (assuming that the input voltage is sufficiently high to allow normal operation).
ch09q08.gif

a) 11 V.
b) 12 V.
c) 15 V.
d) 16 V.


Correct Answer:16 V.




Q-9 Which of the following statements is incorrect?


a) A great advantage of switching regulators is that their power consumption is very low.
b) Switching regulators use switching speeds of 20 kHz or more.
c) The output voltage of a switching regulator is controlled by altering the switching frequency.
d) Both bipolar transistors and FETs have very good switching characteristics.



Correct Answer:The output voltage of a switching regulator is controlled by altering the switching frequency.


Q-10 A power supply that makes use of a switching regulator is referred to as a switch-mode power supply.


a) True
b) False



Correct Answer: True



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