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:
A. 3rd quadrant
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
C. anode lead
D. cathode 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
Question 41
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