Question 1

Figure 1
-Refer to Figure 1. The type of device that is illustrated by this structure is

Accepted Answer

A)  an SCS
B)  a UJT
C)  a diac
D)  none of the aboveE) A) and D)
F) A) and C)

Question 2

A device that can be triggered on or off is

Accepted Answer

A)  a triac
B)  an SCS
C)  both A and B
D)  none of the aboveE) A) and D)
F) B) and C)

Question 3

A SCR can be turned on

Accepted Answer

A)  by exceeding the forward breakover voltage
B)  by forced commutation
C)  both A and B
D)  none of the aboveE) None of the above
F) B) and C)

Question 4

The forward- blocking region of a four- layer diode is from 0 V to VAK = VBR(F).

Accepted Answer

A) True 
 B)False  True

Question 5

An equivalent circuit for a UJT is back- to back npn and pnp transistors.

Accepted Answer

A) True 
 B)False  False

Question 6

Figure 5
-Refer to Figure 5. The signal you expect to see on the oscilloscope is a

Accepted Answer

A)  sine wave
B)  a square wave
C)  modified sawtooth wave
D)  series of positive trigger pulsesE) None of the above
F) All of the above

Question 7

A triac is essentially a bidirectional electronic switch.

Accepted Answer

A) True 
 B)False

Question 8

To stop conduction in an SCR, you could

Accepted Answer

A)  remove gate current
B)  apply a negative pulse to the gate
C)  both A and B
D)  none of the aboveE) A) and B)
F) None of the above

Question 9

Increasing the firing angle in an SCR control circuit

Accepted Answer

A)  increases the SCR current
B)  increases the holding current
C)  increases the output current
D)  none of the aboveE) A) and D)
F) B) and D)

Question 10

Figure 5
-Refer to Figure 5. If the value of R3 is reduced, the output amplitude will _ and the frequency will .

Accepted Answer

A)  decrease, increase
B)  decrease, decrease
C)  increase, decrease
D)  increase, increaseE) A) and B)
F) A) and D)

Question 11

The IH specification is the highest allowed current in a thyristor.

Accepted Answer

A) True 
 B)False

Question 12

The characteristic of a UJT that determines its turn- on point is called the

Accepted Answer

A)  blocking point
B)  standoff ratio
C)  forward breakover voltage
D)  trigger currentE) C) and D)
F) None of the above

Question 13

A diac can conduct current in either direction.

Accepted Answer

A) True 
 B)False

Question 14

A diac will stop conducting if

Accepted Answer

A)  the peak of the applied waveform is reached
B)  low- current dropout occurs
C)  it receives a negative gate voltage
D)  all of the aboveE) C) and D)
F) A) and C) B

Question 15

The number of pn junctions in a UJT is

Accepted Answer

A)  zero
B)  one
C)  two
D)  threeE) B) and C)
F) A) and B)

Question 16

A diac is equivalent to two back- to- back inverted

Accepted Answer

A)  triacs
B)  four- layer diodes
C)  SCRs
D)  SCSsE) A) and B)
F) A) and C)

Question 17

LASCR stands for low- amplitude silicon controlled rectifier.

Accepted Answer

A) True 
 B)False

Question 18

The purpose of an SCR crowbar circuit is to protect a load in case of

Accepted Answer

A)  an open circuit
B)  overvoltage
C)  power failure
D)  all of the aboveE) B) and D)
F) C) and D)

Question 19

The voltage drop across a conducting SCR

Accepted Answer

A)  is half the load voltage
B)  is a small negative voltage
C)  follows the input voltage
D)  is lowE) A) and D)
F) None of the above

Question 20

The forward breakover voltage for an SCR

Accepted Answer

A)  is a constant quantity specified by the manufacturer
B)  is proportional to VAK
C)  is dependent on the maximum specified anode current
D)  decreases for increasing IGE) A) and B)
F) A) and C)

Exam 11: Thyristors

Figure 1 -Refer to Figure 1. The type of device that is illustrated by this structure is

Correct AnswerverifiedShow Answer

A device that can be triggered on or off is

Correct AnswerverifiedShow Answer

A SCR can be turned on

Correct AnswerverifiedShow Answer

The forward- blocking region of a four- layer diode is from 0 V to VAK = VBR(F).

Correct AnswerverifiedTrue

An equivalent circuit for a UJT is back- to back npn and pnp transistors.

Correct AnswerverifiedFalse

Figure 5 -Refer to Figure 5. The signal you expect to see on the oscilloscope is a

Correct AnswerverifiedShow Answer

A triac is essentially a bidirectional electronic switch.

Correct AnswerverifiedShow Answer

To stop conduction in an SCR, you could

Correct AnswerverifiedShow Answer

Increasing the firing angle in an SCR control circuit

Correct AnswerverifiedShow Answer

Figure 5 -Refer to Figure 5. If the value of R3 is reduced, the output amplitude will _ and the frequency will .

Correct AnswerverifiedShow Answer

The IH specification is the highest allowed current in a thyristor.

Correct AnswerverifiedShow Answer

The characteristic of a UJT that determines its turn- on point is called the

Correct AnswerverifiedShow Answer

A diac can conduct current in either direction.

Correct AnswerverifiedShow Answer

A diac will stop conducting if

Correct AnswerverifiedB

The number of pn junctions in a UJT is

Correct AnswerverifiedShow Answer

A diac is equivalent to two back- to- back inverted

Correct AnswerverifiedShow Answer

LASCR stands for low- amplitude silicon controlled rectifier.

Correct AnswerverifiedShow Answer

The purpose of an SCR crowbar circuit is to protect a load in case of

Correct AnswerverifiedShow Answer

The voltage drop across a conducting SCR

Correct AnswerverifiedShow Answer

The forward breakover voltage for an SCR

Correct AnswerverifiedShow Answer

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True

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False

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B

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