Diodes and Applications

Q1: List three diode packages:

A clip package, DIP, small current package

B DIP, small current package, large current package

C small current package, large current package, and SIP

D small current package, large current package, clip package

Q2: The mimicking of an open/closed switch by a diode allows alternating current to be:

A rectified

B regulated

C controlled

D attenuated

Q3: The characteristic curve for the complex model of a silicon diode shows that

A the barrier potential is 0 V

B the barrier potential stays fixed at 0.7 V

C the barrier potential increases slightly with an increase in current

D the barrier potential decreases slightly with an increase in current

Q4: What is wrong with this circuit?

A The zener is open.

B The zener is shorted.

C nothing

D not enough data

Q5: With a half-wave rectified voltage across the load resistor, load current flows for what part of a cycle?

A 0 degrees

B 90 degrees

C 180 degrees

D 360 degrees

Q6: The area at the junction of p-type and n-type materials that has lost its majority carriers is called the

A barrier potential

B depletion region

C
n region

D
p region

Q7: The dc current through each diode in a bridge rectifier equals:

A the load current

B half the dc load current

C twice the dc load current

D one-fourth the dc load current

Q8: With a 12 V supply, a silicon diode, and a 370-ohm resistor in series, what voltage will be dropped across the diode?

A
0.3 V

B
0.7 V

C
0.9 V

D
1.4 V

Q9: What is a varistor?

A a voltage-dependent resistor

B a voltage-dependent diode

C a current-dependent resistor

D a current-dependent diode

Q10: In a power supply diagram, which block indicates a smooth dc output?

A transformer

B filter

C rectifier

D regulator

Q11: A characteristic curve is the result of a current versus voltage plot of diode activity, which begins at the:

A 3rd quadrant

B current plot

C graph origin

D voltage plot

Q12: What is the current through the LED?

A
0 mA

B
23 mA

C
18 mA

D
13 mA

Q13: When matching polarity connections have been made and the potential difference (PD) is above 0.7 V, the diode is considered to be:

A not working

B forward biased

C reverse biased

D an open switch

Q14: Shunting the ac component away from the load is the task of a:

A transformer

B filter

C regulator

D rectifier

Q15: Providing a constant output regardless of ac input or load resistance changes is the function of a:

A transformer

B filter

C regulator

D rectifier

Q16: In a power supply diagram, which block indicates a pulsating dc output?

A transformer

B filter

C rectifier

D regulator

Q17: In a diode schematic, the anode is represented by a(n):

A triangle

B vertical line

C zig-zag line

D element indicator

Q18: With full-wave rectification, current through the load resistor must be:

A in opposite directions

B to the external load

C from the reverse biased diode

D in the same direction

Q19: When a diode is forward biased, the voltage across it

A is directly proportional to the current

B is inversely proportional to the current

C is directly proportional to the source voltage

D remains approximately the same

Q20: What is the percent of regulation if Vnl = 20 V and Vfl = 19.8 V?

A
0%

B
1%

C
.1%

D
5%

Q21: A diode for which you can change the reverse bias, and thus vary the capacitance is called a

A varactor diode

B tunnel diode

C zener diode

D switching diode

Q22: What is wrong with this diode?

A open

B short

C nothing

D not enough data

Q23: Rectifier output polarity depends upon:

A cycles of input

B capacitor polarity

C half or full wave

D diode installation

Q24: What circuit activity may shift a characteristic curve so that diode operating points are different?

A higher power (heat)

B higher resistance

C lower voltage

D lower current

Q25: When checking a diode, low resistance readings both ways indicate the diode is:

A open

B satisfactory

C faulty

D not the problem

Q26: Thermal shutdown occurs in an IC regulator if:

A power dissipation is too high

B internal temperature is too high

C current through the device is too high

D load resistance increases

Q27: What is the peak output voltage for this half-wave rectifier?

A
1 V

B
7.8 V

C
10.9 V

D
15.6 V

Q28: Since diodes are destroyed by excessive current, circuits must have:

A higher voltage sources

B current limiting resistors

C more dopants

D higher current sources

Q29: Why is heat produced in a diode?

A due to current passing through the diode

B due to voltage across the diode

C due to the power rating of the diode

D due to the PN junction of the diode

Q30: A pn junction allows current flow when

A
the p-type material is more positive than the n-type material

B
the n-type material is more positive than the p-type material

C
both the n-type and p-type materials have the same potential

D
there is no potential on the n-type or p-type materials

Q31: The arrow in the schematic symbol of a diode points to

A
the n-type material, which is called the anode

B
the n-type material, which is called the cathode

C
the p-type material, which is called the anode

D
the p-type material, which is called the cathode

Q32: The dc current through each diode in a bridge rectifier equals:

A the load current

B half the dc load current

C twice the dc load current

D one-fourth the dc load current

Q33: The voltage where current may start to flow in a reverse-biased pn junction is called the

A breakdown voltage

B barrier potential

C forward voltage

D biasing voltage

Q34: When a diode is destroyed it has infinite impedance. When damaged by heat it will probably:

A short

B conduct more

C conduct less

D open

Q35: Which of the following circuits would require the least amount of filtering?

A A half-wave rectifier

B A full-wave rectifier

C A bridge rectifier

D A full-wave rectifier and a bridge rectifier

Q36: If a 169.7 V half-wave peak has an average voltage of 54 V, what is the average of two full-wave peaks?

A
119.9 V

B
108.0 V

C
115.7 V

D
339.4 V

Q37: The conduction band is closest to the valence band in

A semiconductors

B conductors

C insulators

D The distance is the same for all of the above.

Q38: A filtered full-wave rectifier voltage has a smaller ripple than does a half-wave rectifier voltage for the same load resistance and capacitor values because:

A there is a shorter time between peaks

B there is a longer time between peaks

C the larger the ripple, the better the filtering action

D none of the above

Q39: What is the current through the diode?

A
1 mA

B
0.975 mA

C
0.942 mA

D
0.0 mA

Q40: What is the current through the zener diode?

mcq11_1011_1.gif

A
0 mA

B
7 mA

C
8.3 mA

D
13 mA

Q41: An IC regulator receives an overload; it will:

A shut down

B compensate for heat

C provide more voltage

D sample and adjust

Q42: At any given time in an intrinsic piece of semiconductor material at room temperature

A electrons drift randomly

B recombination occurs

C holes are created

D All of the above

Q43: The diode schematic arrow points to the:

A trivalent-doped material

B positive axial lead

C anode lead

D cathode lead

Q44: If the frequency of the applied ac signal to a half-wave rectifier is 60 Hz, the frequency of the pulsating dc output will be

A
30 pps

B
60 pps

C
90 pps

D
120 pps

Q45: Testing a good diode with an ohmmeter should indicate

A high resistance when forward or reverse biased

B low resistance when forward or reverse biased

C high resistance when reverse biased and low resistance when forward biased

D high resistance when forward biased and low resistance when reverse biased

Q46: Electrons in the outermost orbit or shell of an atom are called

A free electrons

B negative ions

C valence electrons

D conduction band electrons

Q47: The peak inverse voltage (PIV) across a nonconducting diode in a bridge rectifier equals approximately:

A half the peak secondary voltage

B twice the peak secondary voltage

C the peak value of the secondary voltage

D four times the peak value of the secondary voltage

Q48: DC power should be connected to forward bias a diode as follows:

A
– anode, + cathode

B
– cathode, – anode

C
+ anode, – cathode

D
+ cathode, + anode

Q49: Which type of transformer is required to create a 180 degree input to a rectifier?

A center-tapped secondary

B step-down secondary

C stepped-up secondary

D split winding primary

Q50: When a diode is forward biased, the voltage across it

A is directly proportional to the current

B is inversely proportional to the current

C is directly proportional to the source voltage

D remains approximately the same


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