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terms ^^ > thyristors & tranducers > Flashcards

thyristors & tranducers Flashcards

1
Q

A TRIAC:
can trigger only on positive gate voltages
can trigger only on negative gate voltages
cannot be triggered with gate voltages
can be triggered by either a positive or a negative gate voltage

A

can be triggered by either a positive or a negative gate voltage

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2
Q

When checking a good SCR or TRIAC with an ohmmeter it will:
show high resistance in both directions
show low resistance with positive on anode and negative on cathode, and high resistance when reversed
show high resistance with negative on anode and positive on cathode, and low resistance when reversed
show low resistance in both directions

A

show high resistance in both directions

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3
Q

What does a hall effect sensor sense?
temperature
moisture
magnetic fields
pressure

A

magnetic fields

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4
Q

What causes the piezoelectric effect?
heat or dissimilar metals
pressure on a crystal
water running on iron
a magnetic field

A

pressure on a crystal

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5
Q

A UJT has:
two base leads
one emitter lead
two emitter leads and one base lead
one emitter lead and two base leads

A

one emitter lead and two base leads

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6
Q

The only way to close an SCR is with:
a trigger input applied to the gate
forward breakover voltage
low-current dropout
valley voltage

A

forward breakover voltage

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7
Q

What is an SCR?
a PNPN thyristor with 3 terminals
a PNPN thyristor with 4 terminals
a PNP thyristor with 3 terminals
an NPN thyristor with 3 terminals

A

a PNPN thyristor with 3 terminals

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8
Q

What type of application would use a photovoltaic cell?
an automobile horn
a TI 92 calculator
a magnetic field detector
a remote power source

A

a remote power source

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9
Q

The smallest amount of current that the cathode-anode can have, and still sustain conduction of an SCR is called the:
maximum forward current
maximum forward gate current
holding current
reverse gate leakage current

A

reverse gate leakage current

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10
Q

Once a DIAC is conducting, the only way to turn it off is with:
a positive gate voltage
a negative gate voltage
low-current dropout
breakover

A

low-current dropout

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11
Q

The DIAC is a:
transistor
unidirectional device
three-layer device
bidirectional device

A

bidirectional device

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12
Q

What type of application would use an injection laser diode?
a 10BASE-T Ethernet
a liquid crystal display
a fiber optic transmission line
a good flashlight

A

a fiber optic transmission line

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13
Q

The PUT (programmable unijunction transistor) is actually a type of:
UJT thyristor
FET device
TRIAC
SCR

A

UJT thyristor

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14
Q

A transducer’s function is to:
transmit electrical energy
convert energy
produce mechanical energy
prevent current flow

A

convert energy

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15
Q

The ________ can be externally programmed to turn on at a desired anode-to-gate voltage level.
UJT
PUT
SCR
SCS

A

PUT

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16
Q

You need a very efficient thyristor to control the speed of an AC fan motor. A good device to use would be
a 4-layer diode.
a PUT.
a triac.
a BJT.

A

a triac

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17
Q

An application of a(n) ________ is in a lighting system for power interruptions.
SCR
SCS
diac
triac

A

SCR

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18
Q

The silicon-controlled switch (SCS) is similar in construction to the
triac.
diac.
SCR.
4-layer diode.

A

SCR

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19
Q

The ________ can conduct current in either direction and is turned on when a breakover voltage is exceeded.
SCR
diac
SCS
triac

A

diac

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20
Q

You need to design a relaxation oscillator circuit. The most likely device to use might be
an SCR.
a UJT.
a triac.
a 4-layer diode.

A

a UJT

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21
Q

You have the schematic diagram of several types of circuits. Which of these circuits most likely uses a triac?
an oscillator
an ac motor control
a programmable oscillator
an amplifier

A

an ac motor control

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22
Q

The ________ is like a diac with a gate terminal.
triac
SCR
SCS
none of the above

A

triac

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23
Q

You have a need to use a device to trigger an SCR. A good one to use might be
an SCS.
a UJT.
a 4-layer diode.
a PUT.

A

a UJT

24
Q

The SCR can be triggered on by a pulse at the
gate.
anode.
cathode.
none of the above

A

gate

25
Q

Which of the following devices might best be used to control an electric motor?
an SCS
a PUT
an SCR
a diac

A

a SCR

26
Q

You have a light-dimmer circuit using an SCR. In testing the circuit, you find that IG = 0 mA and the light is still on. You conclude that the trouble might be one of the following:
the SCR is open.
the switch is faulty.
the gate circuit is shorted.
this is normal; nothing is wrong.

A

this is normal; nothing is wrong.

27
Q

How many semiconductor layers are thyristors constructed with?
2
3
4
5

A

4

28
Q

Your boss has asked you to recommend a thyristor that will enable you to turn it on with a pulse and also turn it off with a pulse. Which of the following should you recommend?
an SCR
an SCS
a PUT
a triac

A

an SCS

29
Q

An SCR acts to control the speed of an electric motor by ________ the ________ of the pulse delivered to the motor.
varying, width
increasing, amplitude
decreasing, gate width
none of these

A

varying, width

30
Q

Which of the following devices does not have a cathode terminal?
SCR
SCS
Triac
Shockley diode

A

Triac

31
Q

Which of the following devices is unquestionably of the greatest interest today?
SCR
GTO
LASCR
SCS

A

SCR

32
Q

Which of the following devices has a negative-resistance region in its characteristics curve?
SCR
SCS
Unijunction transistor
Phototransistor

A

Unijunction transistor

33
Q

How many terminals does a programmable unijunction transistor (PUT) have?
4
3
2
1

A

3

34
Q

What is the typical value of the reverse resistance of SCRs?
1 to 10
100 to 1 k
1 k to 50 k
100 k or more

A

100 k or more

35
Q

The ISO-LIT Q1 16-pin Litronix opto-isolator DIP contains ________ opto-isolators.
4
8
12
6

A

4

36
Q

How many terminals does a Shockley diode have?
5
4
3
2

A

2

37
Q

What is the range of the variable resistor in the equivalent circuit of a unijunction transistor?
50 to 5 k
6 k to 10 k
5 to 50
1 to 5

A

50 to 5 k

38
Q

Which one of the SCR terminals fires the SCR?
Anode
Cathode
Gate
All of the above

A

Gate

39
Q

Which of the following devices has the smallest turn-off time?
SCR
GTO
SCS
LASCR

A

GTO

40
Q

What is the range of the turn-on times in high-power SCR devices?
30 s to 100 s
10 s to 25 s
5 s to 8 s
1 s to 5 s

A

10 s to 25 s

41
Q

What is the frequency range of application of SCRs?
About 10 kHz
About 50 kHz
About 250 kHz
About 1 mHz

A

About 50 kHz

42
Q

Which of the following devices has nearly the same turn-on time as turn-off time?
SCR
GTO
SCS
LASCR

A

GTO

43
Q

Which of the transistors of an SCR are conducting when the SCR is fired and is in the conduction mode?
npn
pnp
Both npn and pnp
Neither npn nor pnp

A

Both npn and pnp

44
Q

For an SCS, a ________ pulse at the anode gate turns the device on, while a ________ pulse will turn it off.
negative, positive
positive, negative

A

negative, positive

45
Q

Which of the following devices has (have) four layers of semiconductor materials?
Silicon-controlled switch (SCS)
Gate turn-off switch (GTO)
Light-activated silicon-controlled rectifier (LASCR)
All of the above

A

All of the above

46
Q

Which of the following parameters are usually provided by the manufacturer on the specification sheet for SCRs?
Turn-on time (ton )
Turn-off time (toff )
Junction and case temperatures (tj and tc )
All of the above

A

All of the above

47
Q

What is the maximum current (rms) rating for commercially available LASCRs today?
3 A
15 A
20 A
25 A

A

3 A

48
Q

Which of the following areas is (are) applications of an SCS?
Counters
Pulse generators
Voltage sensors
All of the above

A

All of the above

49
Q

How many terminals does a silicon-controlled switch (SCS) device have?
2
3
4
5

A

4

50
Q

What is the typical value of the triggering anode gate for SCS devices?
1.5 mA
150 A
15 A
1 A

A

1.5 mA

51
Q

What is the typical range of turn-off times for SCRs?
5u s to 30u s
1 s to 5 s
0.1 s to 1 s
0.01 s to 0.1 s

A

5 uS to 30 us

52
Q

Which of the following is (are) the advantages of the SCS over a corresponding SCR?
Reduced turn-off time
Increased control and triggering sensitivity
More predictable firing situation
All of the above

A

All of the above

53
Q

Which of the following transistors is an SCR composed of?
npn, pnp
npn, npn
pnp, pnp
None of the above

A

npn, pnp

54
Q

A thyristor is a ________-layer semiconductor material device.
2
3
4
5

A

4

55
Q

How many layers of semiconductor materials does a silicon-controlled rectifier (SCR) have?
2
3
4
5

A

4

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