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Diodes and Applications MCQ Questions & Answers

Diodes and Applications MCQs : This section focuses on the "Diodes and Applications". These Multiple Choice Questions (MCQs) should be practiced to improve the Diodes and Applications skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.




Question 1

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

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Question 2

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

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Question 3

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

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Question 4

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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Question 5

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

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Question 6

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

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Question 7

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.

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Question 8

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

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Question 9

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

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Question 10

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

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Question 11

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

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Question 12

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

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Question 13

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

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Question 14

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

A. transformer
B. filter
C. rectifier
D. regulator

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Question 15

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

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Question 16

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

A. 0%
B. 1%
C. 0.10%
D. 5%

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Question 17

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

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Question 18

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

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Question 19

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

A. transformer
B. filter
C. rectifier
D. regulator

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Question 20

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

A. triangle
B. vertical line
C. zig-zag line
D. element indicator

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Question 21

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

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Question 22

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

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Question 23

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

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Question 24

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

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Question 25

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

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Question 26

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

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Question 27

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

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Question 28

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

A. transformer
B. filter
C. regulator
D. rectifier

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Question 29

What is a varistor?

A. a voltage-dependent resistor
B. a voltage-dependent diode
C. a current-dependent resistor
D. a current-dependent diode

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Question 30

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

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Question 31

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

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Question 32

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

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Question 33

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

A. – anode, + cathode
B. – cathode, – anode
C. #NAME?
D. + cathode, + anode

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Question 34

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

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Question 35

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

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Question 36

Rectifier output polarity depends upon:

A. cycles of input
B. capacitor polarity
C. half or full wave
D. diode installation

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Question 37

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

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Question 38

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

A. open
B. satisfactory
C. faulty
D. not the problem

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Question 39

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

A. rectified
B. regulated
C. controlled
D. attenuated

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Question 40

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

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Question 41

The diode schematic arrow points to the:

A. trivalent-doped material
B. positive axial lead
C. anode lead
D. cathode lead

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