# 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 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

Question 2

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

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

Question 3

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

Question 4

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

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

Question 5

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

Question 6

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

Question 7

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

Question 8

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.

Question 9

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

Question 10

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

Question 11

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

Question 12

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

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

Question 13

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

B. current plot
C. graph origin
D. voltage plot

Question 14

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

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

Question 15

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

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

Question 16

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

Question 17

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

Question 18

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

Question 19

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

Question 20

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

Question 21

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

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

Question 22

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

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

Question 23

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

Question 24

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

Question 25

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

Question 26

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

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

Question 27

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

Question 28

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

Question 29

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

Question 30

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

Question 31

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

Question 32

The diode schematic arrow points to the:

A. trivalent-doped material
B. positive axial lead

Question 33

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

Question 34

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

Question 35

What is a varistor?

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

Question 36

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

Question 37

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

Question 38

Rectifier output polarity depends upon:

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

Question 39

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

Question 40

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