Important MCQ with solutions
1.A pure semiconductor is often referred to as
2.In a p-type semiconductor, the majority current Carriers are
3. A diode is a
4.A p-type semiconductor is a semiconductor doped with
A) trivalent impurity
B)pentavalent impurity atoms
C)impurity atoms whose electron valence is + 4
D)none of the above
5.What is the DC output voltage of an unfiltered half wave rectifier whos peak output voltage is 9.8 volt
A) 6.23 volt
B) 19.6 volt
C) 9.8 volt
D) 3.1 volt
(Hint : Vdc =0.318 * Vo/p(pk))
6.In n-type semiconductor the minority current carriers are
7.To a first approximation a forward biased diode is treated like a
A) open switch with infinite resistance
B) closed switch with the voltage drop of zero volt
C) close switch in series with the battery voltage of 0.7 volt
D) lose switch in series with a small resistance and a battery
8.What is the frequency of the capacitor ripple voltage in a full wave rectifier circuit if the frequency of the transformer secondary voltage is 60 Hertz
A) 60 Hertz
B) 120 Hertz
(Hint : F(out)=2 F(in))
C) 50 Hertz
D) be this is impossible to determine
9.In a full wave rectifier the DC load current equals 1 ampere, how much DC current is carried by each diode
A) 1/2 A
(Hint: I(diode)=I(load)/2)
B) 1 ampere
C)2 ampere
D)0 Ampere
10.An n-type semiconductor is a semiconductor that has been doped with
A) trivalent impurity atoms
C) impurity atoms whose electrons valence is + 4
D) none
11. For a silicon diode the barrier potential Vb is approximately equal to
A) 0.3 volt
B) 0.7 volt
C) 6.8 volt
D) 2.0 volt
12. To forward biased diode
A) the cathode voltage must be positive with respect to the anode
B) the anode voltage must be positive with respect to its cathode
C) the anode voltage must be negative with respect to its cathode
D) none of the above
13. The sharing of valence electron in a silicon crystal is called
A) doping
B) coupling
C) covalent bonding
D) the avalanche effect
14. Reverse bias diode acts like
A) open switch
B) close switch
C) small resistance
D) none of the above
15. When used as a voltage regulator, zener diode is normally
A) not baised
B) forward biased
C) reverse biased
D) none of the above
16. For a germanium diode, the barrier potential is
A) 0.3 volt
B) 0.3 eV
C) 0.7 volt
D) 0.7 eV
17.In a loaded zener regulator , the series resistor has a current of 120 mA , if the load current is 45 mA .How much is the zener current ?
A) 75 mA
(Hint : Iz =Is – I(load))
B) 45 mA
C) 165 mA
D) this is impossible to determine
18. The approximate voltage drop across a forward biased LED is
A) 0.3 volt
B) 2.0 volt
C) 5.6 volt
D) 0.7 volt
19. The output from an unfiltered half wave or full wave rectifier is a
A) smooth DC voltage
B) steady DC voltage
C) pulsating DC voltage
D) AC voltage
20.A 12 volt zener diode has a 1 watt power rating , what is the maximum rated zener current ?
A) 1 ampere
B) 46.1 milliampere
C) 83.3 milliampere
(Hint: I=P/V)
D) 120 milliampere
21. If the arrow of the Crystal diode symbol is positive with respect to bar , then the diode is ….
22.In the breakdown region ,a zener diode behaves like a …. source
A) constant voltage
B) constant current
C) constant resistance
D) none of the above
23. If the temperature of Crystal diode increases ,the leakage current…
A) remains the same
B) decreases
C) increases
D) become zero
24. When the crystal current diode is large , the bias is
A) forward
B) inverse
C) poor
D) reverse
25. for the same secondary voltage , output voltage from a centre tap rectifier is….. than that of bridge rectifier.
A) twice
B) thrice
C) one half
D) four times
26. Zener diode is used as
A) an amplifier
B) a voltage regulator
C) a multivibrator
D) a rectifier
27. The disadvantage of a half wave rectifier is that the
A) components are expensive
B) diodes must have a higher power rating
C) output is difficult to filter
D) none of the above
28. A zener diode has … breakdown voltage
A) undefined
B) zero
C) sharp
D) none of the above
29. Zener diode is always… connected
A) reverse
B) either reverse or forward
C) forward
D) none of the above
30. A 10 volt power supply would use as ……filter capacitor
A) electrolytic capacitor
B) mica capacitor
C) paper capacitor
D) air capacitor
31. The…. filter circuit results in the best voltage regulation
A) choke input
B) capacitor input
C) resistance input
D) none of the above
32. If the PIV rating of a diode is exceeded,…..
A) the diode conducts poorly
B) the diode is destroyed
C) the diode behaves like a zener diode
D) none of the above
33. Zener diode is destroyed if it…
A) is forward biased
B) is reverse biased
C) carries more than the rated current
D) none of the above
34. If the doping level of a crystal diode is increased ,the breakdown voltage
A) remains the same
B) is increased
C) is decreased
D) none of the above
35. Mains AC power is converted into DC power for
A) lightning purpose
B) heaters
C) using in electronics equipments
D) none of the above
36. The ripple factor of a half wave rectifier is…
A) 2
B) 1.21
C) 2.5
D) 0.48
37. The maximum efficiency of a half wave rectifier is…….
A) 40.6%
B) 81.2%
C) 50%
D) 25%
38. The most widely used rectifier is
A) half wave rectifier
B) centre-tap full wave rectifier
C) bridge full-wave rectifier
D) none of the above
39. Zener diode has…
A) 1 PN junction
B) 2 PN junction
C) 3 PN junction
D) 4 PN junction
40. Avalanche breakdown in a crystal diode occurs when
A) the potential barrier is reduced to zero
B) forward current exceeds a certain value
C) reverse bias exceeds a certain value
D) none of the above
41.When crystal diode is used as a rectifier, the most important consideration is….
A) forward characteristic
B) doping level
C) reverse characteristic
D) PIV rating
42. When the graph between current through and voltage across a device is a straight line , the device is referred to a
A) linear
B) active
C) nonlinear
D) passive
43. The leakage current in a crystal diode is due to
B) majority charge carriers
C) junction capacitance
D) none of the above
44. The PIV rating of a crystal diode is…. …..that of equivalent vacuum diode
A) same as
B) lower than
C) more than
D) none of the above
45. The knee voltage of a crystal diode is approximately equal to..
A) barrier potential
B) breakdown voltage
C) applied voltage
D) forward voltage
46.If the doping level in a crystal diode is increased , the width of depletion layer
A) remains the same
B) is increased
C) is decreased
D) none of the above
47. The doping level in a zener diode is …………………………… that of a crystal diode
A) same as
B) more than
C) less than
D) none of the above
48. A series resistance is connected in the zener circuit to…
A) protect the zener diode
B) properly reverse bias the zener
C) properly forward bias the zener
D) none of the above
49. zener diode is a …. device
A) non-linear
B) linear
C) amplifying
D) none of the above
50. In a half wave rectifier ,the load current flows for
A) the complete cycle of input signal
B) only for positive half cycle of the input signal
C) less than half cycle of the input signal
D) more than half cycle but less than the complete cycle of input signal