Level 3 Electronics Exam Questions With Complete
Solutions
A controlled rectifier circuit requires phase control up to 150
degrees, Describe the triggering circuit needed Correct Answers
A triggering circuit with the resistance and capacitance will be
required
A Diac/Triac package is frequently used in what device Correct
Answers Light Dimmers
A SCR is
A) Unidirectional
B) Bidirectional
C) Tridirectional Correct Answers A ) Unidirectional
An LASCR may have how many leads? Why? Correct Answers
Two or Three, the gate may be used to adjust light sensitivity
An SCR is a _________ layer, _______ junction device Correct
Answers 4 layer, 3 junction
An SCR, compared to an electromechanical device, would be
called a Correct Answers Latching Relay
BJT (Bipolar Junction Transistor) can be used for two different
purposes, what are they? Correct Answers Switch and
Amplifier
, Comparing Triacs and SCRs, which one operates at lower
frequency? Correct Answers Triacs
Describe the connection require for SCRs to provide full phase
control Correct Answers Inverse Parallel
Describe two circuit connections to naturally commutate an SCR
Correct Answers NC switch in series with A-K or NO switch in
parallel to A-K
Describe what natural commutation means with respect to an
SCR? Correct Answers Anode to Kathode current is
interrupted
Does a Triac have a Reverse Breakover Voltage rating? Correct
Answers No
Does a Triac need a gate protection Diode? Correct Answers
No
Explain holding current with respect to SCRs Correct Answers
Once an SCR has been fired into conduction, it will not shut off
until the A-K current falls below the value of Ihold
Explain two methods of causing an SCR to conduct from A to K
Correct Answers Exceed forward breakover voltage, or trigger
the gate
Explain why barrier voltage must be overcome for a diode to
conduct Correct Answers Electron/Hole pairing leaves a
neutral depletion zone
Solutions
A controlled rectifier circuit requires phase control up to 150
degrees, Describe the triggering circuit needed Correct Answers
A triggering circuit with the resistance and capacitance will be
required
A Diac/Triac package is frequently used in what device Correct
Answers Light Dimmers
A SCR is
A) Unidirectional
B) Bidirectional
C) Tridirectional Correct Answers A ) Unidirectional
An LASCR may have how many leads? Why? Correct Answers
Two or Three, the gate may be used to adjust light sensitivity
An SCR is a _________ layer, _______ junction device Correct
Answers 4 layer, 3 junction
An SCR, compared to an electromechanical device, would be
called a Correct Answers Latching Relay
BJT (Bipolar Junction Transistor) can be used for two different
purposes, what are they? Correct Answers Switch and
Amplifier
, Comparing Triacs and SCRs, which one operates at lower
frequency? Correct Answers Triacs
Describe the connection require for SCRs to provide full phase
control Correct Answers Inverse Parallel
Describe two circuit connections to naturally commutate an SCR
Correct Answers NC switch in series with A-K or NO switch in
parallel to A-K
Describe what natural commutation means with respect to an
SCR? Correct Answers Anode to Kathode current is
interrupted
Does a Triac have a Reverse Breakover Voltage rating? Correct
Answers No
Does a Triac need a gate protection Diode? Correct Answers
No
Explain holding current with respect to SCRs Correct Answers
Once an SCR has been fired into conduction, it will not shut off
until the A-K current falls below the value of Ihold
Explain two methods of causing an SCR to conduct from A to K
Correct Answers Exceed forward breakover voltage, or trigger
the gate
Explain why barrier voltage must be overcome for a diode to
conduct Correct Answers Electron/Hole pairing leaves a
neutral depletion zone
