PRELIM EXAM  c) It can toggle between two

circuits.
1. What is a mechanical switch
primarily used for?  d) It is used for circuit
protection.
 a) Amplifying electrical signals
Answer: b) It returns to its default position
 b) Connecting and
after being released.
disconnecting electrical circuits
Types and Applications of Mechanical
 c) Storing electrical energy
Switches
 d) Converting electrical energy
1. Which type of mechanical switch
into mechanical energy
is commonly used in household
Answer: b) Connecting and disconnecting light controls?
electrical circuits
 a) Slide switch
1. Which of the following is NOT a
 b) Rotary switch
type of mechanical switch?
 c) Toggle switch
 a) Toggle switch
 d) DIP switch
 b) Push-button switch
Answer: c) Toggle switch
 c) Reed switch
1. What is a crucial feature of a
 d) Proximity switch
micro switch (also known as a
Answer: d) Proximity switch snap-action switch)?

1. What characterizes a single-pole,  a) It requires a large amount of

single-throw (SPST) switch? force to actuate.

 a) It has two positions and  b) It operates with a small force

controls two circuits. and provides a quick switching
action.
 b) It has one input and one
output, allowing or interrupting  c) It is used only in high-voltage
a circuit. applications.

 c) It can switch between  d) It has no moving parts.

multiple outputs.
Answer: b) It operates with a small force
 d) It is used for alternating and provides a quick switching action.
current (AC) only.
1. In which application would you
Answer: b) It has one input and one output, most likely find a rotary switch?
allowing or interrupting a circuit.
 a) Controlling the speed of a
1. In a double-pole, double-throw ceiling fan
(DPDT) switch, how many circuits
 b) Operating a doorbell
can be controlled?
 c) Turning on a light bulb
 a) One
 d) Resetting a circuit breaker
 b) Two
Answer: a) Controlling the speed of a ceiling
 c) Three
fan
 d) Four
1. What distinguishes a maintained
Answer: b) Two switch from a momentary switch?

1. Which of the following describes  a) A maintained switch stays in

the primary function of a the last position until manually
momentary switch? changed, while a momentary
switch returns to its default
 a) It stays in the "on" position position.
after being pressed.
 b) A momentary switch stays in
 b) It returns to its default the last position until manually
position after being released. changed, while a maintained
 switch returns to its default 1. Which type of mechanical switch
position. is typically used in safety
interlock systems?
 c) A maintained switch requires
continuous pressure to operate.  a) Toggle switch
 d) A maintained switch is  b) Push-button switch
typically used in high-current
 c) Limit switch
applications only.
 d) Rotary switch
Answer: a) A maintained switch stays in the
last position until manually changed, while a Answer: c) Limit switch
momentary switch returns to its default
position. 1. Which factor is least likely to
affect the longevity of a
Safety and Performance mechanical switch?
1. Which of the following is a key  a) The frequency of operation
consideration when selecting a
mechanical switch for an  b) The ambient temperature
application?  c) The color of the switch casing
 a) The color of the switch  d) The electrical load applied to
 b) The type of signal it amplifies the switch

 c) The current and voltage Answer: c) The color of the switch casing
rating of the switch Mechanical Switches: Design and
 d) The brand of the Characteristics
switchAnswer: c) The current 1. Which of the following mechanical
and voltage rating of the switch switches is known for providing
2. Why is debounce circuitry or tactile feedback to the user?
software often used with  a) Toggle switch
mechanical switches?
 b) Membrane switch
 a) To increase the current
capacity of the switch  c) Mechanical keyboard switch

 b) To filter out false signals  d) DIP switch

caused by mechanical bounce
2. Answer: c) Mechanical keyboard
 c) To extend the lifespan of the switch
switch
3. What is the typical application of
 d) To reduce the physical size of a DIP (Dual In-line Package)
the switch switch?

3. Answer: b) To filter out false signals  a) Controlling industrial

caused by mechanical bounce machinery

4. In a mechanical switch, what does  b) Setting configurations on

the term "actuation force" refer printed circuit boards (PCBs)
to?
 c) Operating household
 a) The voltage required to appliances
operate the switch
 d) Switching high-current loads
 b) The amount of force needed
4. Answer: b) Setting configurations on
to move the switch from one
printed circuit boards (PCBs)
position to another
5. In a push-button switch, what is
 c) The speed at which the
the difference between a
switch operates
"normally open" (NO) and
 d) The resistance the switch "normally closed" (NC)
provides to current flow configuration?

Answer: b) The amount of force needed to  a) NO means the circuit is

move the switch from one position to another closed when the button is
 pressed, while NC means the 3. What is the primary benefit of
circuit is open when the button using a limit switch in industrial
is pressed. automation?
 b) NO means the circuit is open  a) It can switch between
when the button is pressed, multiple power sources.
while NC means the circuit is
 b) It provides precise position
closed when the button is
detection and feedback.
pressed.
 c) It can handle high-frequency
 c) NO refers to the voltage
signals.
rating, while NC refers to the
current rating.  d) It offers wireless
communication capabilities.
 d) NO and NC have no
functional differences. 4. Answer: b) It provides precise
position detection and feedback.
6. Answer: b) NO means the circuit is
open when the button is pressed, 5. Which type of mechanical switch
while NC means the circuit is closed would you use in a safety-critical
when the button is pressed. application to ensure the circuit
remains open unless the switch is
7. Which material is most commonly
deliberately activated?
used for the contacts of high-
durability mechanical switches?  a) Push-button switch
 a) Copper  b) Key switch
 b) Aluminum  c) Toggle switch
 c) Silver  d) DIP switch
 d) Plastic 6. Answer: b) Key switch
8. Answer: c) Silver 7. In a mechanical switch used in
harsh environments, what feature
9. What is the purpose of a "travel
is most important for ensuring
distance" specification in a
reliability?
mechanical switch?
 a) Low actuation force
 a) To measure the speed of
actuation  b) High voltage rating
 b) To determine how far the  c) Sealed design to protect
actuator must move to change against dust and moisture
states
 d) Large physical size
 c) To indicate the voltage drop
across the switch 8. Answer: c) Sealed design to protect
against dust and moisture
 d) To specify the current rating
Mechanical Switches in Electronic
10.Answer: b) To determine how far the Circuits
actuator must move to change states
1. Why is gold plating sometimes
Application-Specific Mechanical used on the contacts of
Switches mechanical switches?
1. Which of the following mechanical  a) To increase the physical
switches is commonly used in strength of the switch
automotive applications for
detecting door positions?  b) To enhance electrical
conductivity and prevent
 a) Limit switch oxidation
 b) Toggle switch  c) To reduce the cost of the
switch
 c) Micro switch
 d) To improve the mechanical
 d) Rotary switch
durability
2. Answer: c) Micro switch
2. Answer: b) To enhance electrical 11.Which of the following describes
conductivity and prevent oxidation the function of an "interlock" in a
mechanical switch system?
3. Which of the following is a key
advantage of using a mechanical  a) It allows multiple switches to
switch in a circuit over a operate simultaneously.
semiconductor switch?
 b) It prevents a switch from
 a) Faster switching speed being activated under certain
conditions.
 b) Higher resistance to wear
and tear  c) It reduces the physical size of
the switch.
 c) Greater robustness in high-
voltage applications  d) It increases the current-
carrying capacity of the switch.
 d) Lower power consumption
12.Answer: b) It prevents a switch from
4. Answer: c) Greater robustness in
being activated under certain
high-voltage applications
conditions.
5. What is the role of a "spring" in a
Basic Concepts of Electronic Switches
mechanical switch design?
1. Which of the following is an
 a) To reduce contact resistance
example of an electronic switch?
 b) To provide tactile feedback
 a) Relay
 c) To return the actuator to its
 b) Transistor
default position
 c) Toggle switch
 d) To enhance electrical
conductivity  d) Micro switch
6. Answer: c) To return the actuator to 2. Answer: b) Transistor
its default position
3. What is the primary function of an
7. Which type of mechanical switch electronic switch in a circuit?
would you choose for a user
 a) To increase the voltage of a
interface that requires frequent,
circuit
rapid actuation?
 b) To amplify signals
 a) Toggle switch
 c) To control the flow of current
 b) Micro switch
electronically
 c) Rotary switch
 d) To convert AC to DC
 d) Membrane switch
4. Answer: c) To control the flow of
8. Answer: b) Micro switch current electronically
9. What is the primary reason for 5. Which type of electronic switch is
using a multi-position rotary commonly used for switching
switch in electronic equipment? high-power loads?
 a) To provide a single on/off  a) Bipolar Junction Transistor
function (BJT)
 b) To select between multiple  b) Field-Effect Transistor (FET)
circuits or functions
 c) Thyristor
 c) To act as a backup power
 d) Diode
switch
6. Answer: c) Thyristor
 d) To increase the speed of
signal transmission 7. In a MOSFET (Metal-Oxide-
Semiconductor Field-Effect
10.Answer: b) To select between multiple
Transistor), what controls the flow
circuits or functions
of current between the drain and
source terminals?
  a) The gate voltage  d) Push-button Switch
 b) The source voltage 6. Answer: b) SCR (Silicon-Controlled
Rectifier)
 c) The drain voltage
7. Which of the following devices is
 d) The base current
used to convert a small input
8. Answer: a) The gate voltage voltage into a larger output
voltage in a switching power
9. Which electronic component can supply?
act as both an amplifier and a
switch?  a) Diode

 a) Capacitor  b) Transistor

 b) Inductor  c) MOSFET

 c) Transistor  d) Inductor

 d) Resistor 8. Answer: c) MOSFET

10.Answer: c) Transistor Electronic Switches in Circuit Design

Types and Applications of Electronic 1. What is the purpose of a "pull-up"

Switches resistor in a circuit with an
electronic switch?
1. Which type of electronic switch is
often used in digital circuits to  a) To increase the current flow
switch signals on and off? through the switch

 a) Relay  b) To ensure the switch has a

defined logic level when not
 b) JFET (Junction Field-Effect activated
Transistor)
 c) To reduce the voltage across
 c) CMOS (Complementary the switch
Metal-Oxide-Semiconductor)
 d) To protect the switch from
 d) SCR (Silicon-Controlled overcurrent
Rectifier)
2. Answer: b) To ensure the switch has a
2. Answer: c) CMOS (Complementary defined logic level when not activated
Metal-Oxide-Semiconductor)
3. Which of the following is a key
3. What is the advantage of using a characteristic of a "normally
solid-state relay (SSR) over an open" (NO) electronic switch?
electromechanical relay (EMR)?
 a) It allows current to flow when
 a) SSRs can handle higher no signal is applied.
currents.
 b) It remains open until a
 b) SSRs have no moving parts, control signal is applied.
resulting in faster switching and
longer life.  c) It always conducts current
regardless of the control signal.
 c) SSRs are less expensive.
 d) It has a lower resistance
 d) SSRs are easier to wire. when open.
4. Answer: b) SSRs have no moving 4. Answer: b) It remains open until a
parts, resulting in faster switching and control signal is applied.
longer life.
5. In a transistor switch circuit, what
5. Which electronic switch is best happens when the transistor is
suited for controlling AC power in "saturated"?
lighting dimmers?
 a) It operates in a linear region
 a) NPN Transistor and amplifies the signal.
 b) SCR (Silicon-Controlled  b) It is fully on, allowing
Rectifier) maximum current to flow from
 c) SPST Switch collector to emitter.
  c) It is fully off, preventing any 3. In which situation would you most
current from flowing. likely use a "triac" as an electronic
switch?
 d) It operates in the cutoff
region.  a) In low-power DC circuits
6. Answer: b) It is fully on, allowing  b) In high-frequency
maximum current to flow from communication circuits
collector to emitter.
 c) In AC power control
7. Which of the following describes a applications, such as dimmers
"latching" electronic switch? or motor speed controllers
 a) It automatically returns to its  d) In RF (Radio Frequency)
default state after being signal amplification
activated.
4. Answer: c) In AC power control
 b) It remains in its activated applications, such as dimmers or
state until a reset signal is motor speed controllers
applied.
5. What is a common issue with
 c) It requires a continuous signal electronic switches when used in
to remain in the on state. high-power applications without
proper heat management?
 d) It switches states randomly.
 a) Increased switching speed
8. Answer: b) It remains in its activated
state until a reset signal is applied.  b) Excessive heat generation
leading to failure
9. What is the purpose of a "flyback
diode" in a circuit with an  c) Improved efficiency
inductive load and an electronic
 d) Decreased voltage rating
switch?
6. Answer: b) Excessive heat generation
 a) To increase the switching
leading to failure
speed
7. Why is a "Schmitt trigger" often
 b) To prevent voltage spikes
used in circuits with electronic
caused by the collapsing
switches?
magnetic field
 a) To improve the linearity of
 c) To reduce power consumption
the switch
 d) To amplify the control signal
 b) To create a bistable switch
10.Answer: b) To prevent voltage spikes
 c) To eliminate noise and
caused by the collapsing magnetic
provide clean switching
field
 d) To reduce the power
Performance and Safety in Electronic
consumption of the switch
Switches
8. Answer: c) To eliminate noise and
1. Which type of electronic switch is
provide clean switching
known for its ability to handle
high frequencies with minimal 9. What is the function of an
power loss? "optocoupler" in an electronic
switch circuit?
 a) Relay
 a) To amplify the control signal
 b) BJT (Bipolar Junction
Transistor)  b) To provide electrical isolation
between the control and load
 c) MOSFET
circuits
 d) SCR (Silicon-Controlled
 c) To increase the switching
Rectifier)
speed
2. Answer: c) MOSFET
 d) To decrease the current
through the switch
 10.Answer: b) To provide electrical 4. Which of the following terminals
isolation between the control and load in an SCR controls its switching
circuits action?
11.Which electronic switch would you o a) Anode
choose for a high-speed digital
circuit where power efficiency is o b) Cathode
critical? o c) Gate
 a) Relay o d) Drain
 b) Triac Answer: c) Gate
 c) CMOS transistor 5. What happens when the gate of
 d) BJT transistor an SCR is triggered?

12.Answer: c) CMOS transistor o a) The SCR becomes reverse

biased.
Basic Concepts of Thyristors and SCRs
o b) The SCR switches on and
1. What is a thyristor? allows current to flow from
o a) A four-layer semiconductor anode to cathode.
device used for amplifying o c) The SCR remains off
signals regardless of the gate signal.
o b) A four-layer semiconductor o d) The SCR amplifies the gate
device that acts as a switch signal.
o c) A two-layer diode that Answer: b) The SCR switches on and allows
rectifies AC to DC current to flow from anode to cathode.
o d) A transistor used for high- Types and Applications of Thyristors
frequency applications and SCRs
Answer: b) A four-layer semiconductor 6. In which of the following
device that acts as a switch applications would you typically
find an SCR?
2. Which of the following is a
characteristic of an SCR (Silicon- o a) Digital signal processing
Controlled Rectifier)?
o b) AC motor speed control
o a) It can conduct current in both
directions. o c) Low-power radio transmitters

o b) It remains off until a gate o d) Microprocessor-based

signal is applied. systems

o c) It requires continuous gate Answer: b) AC motor speed control

current to stay on. 7. Which of the following is NOT a
o d) It is primarily used for type of thyristor?
amplifying low-power signals. o a) TRIAC
Answer: b) It remains off until a gate signal o b) DIAC
is applied.
o c) GTO (Gate Turn-Off Thyristor)
3. How many terminals does an SCR
have? o d) BJT (Bipolar Junction
Transistor)
o a) Two
Answer: d) BJT (Bipolar Junction Transistor)
o b) Three
8. What distinguishes a TRIAC from
o c) Four an SCR?
o d) Five o a) A TRIAC can control power in
Answer: b) Three both directions, while an SCR
controls power in only one
direction.
 o b) A TRIAC requires a 12.How can an SCR be turned off
continuous gate signal, while an after it has been turned on?
SCR does not.
o a) By applying a negative gate
o c) A TRIAC is used for DC voltage
applications, while an SCR is
o b) By reducing the current
used for AC applications.
below the holding current
o d) A TRIAC has only two
o c) By increasing the gate
terminals, while an SCR has
current
three.
o d) By short-circuiting the anode
Answer: a) A TRIAC can control power in
both directions, while an SCR controls power and cathode
in only one direction. Answer: b) By reducing the current below
9. Which application would most the holding current
likely use a GTO (Gate Turn-Off 13.In a phase-controlled rectifier
Thyristor)? using an SCR, how is the output
o a) Low-power signal voltage controlled?
amplification o a) By adjusting the frequency of
o b) High-voltage DC transmission the input AC supply
o b) By changing the firing angle
o c) Audio frequency modulation
of the SCR
o d) Battery-operated devices
o c) By varying the load
Answer: b) High-voltage DC transmission resistance
10.Why are SCRs commonly used in o d) By using a feedback control
controlled rectifiers? loop
o a) They have a high switching Answer: b) By changing the firing angle of
frequency. the SCR
o b) They can handle large 14.Which of the following methods is
currents and voltages with commonly used to protect an SCR
precise control. from overvoltage?

o c) They are more efficient than o a) Using a snubber circuit

diodes.
o b) Increasing the gate current
o d) They provide electrical
o c) Adding a heatsink
isolation between circuits.
o d) Reducing the load current
Answer: b) They can handle large currents
and voltages with precise control. Answer: a) Using a snubber circuit
Operation and Control of Thyristors and 15.What is the primary function of a
SCRs DIAC in triggering a TRIAC?
11.What is the "holding current" in o a) To amplify the gate signal
an SCR?
o b) To provide voltage feedback
o a) The minimum current
required to turn the SCR on. o c) To allow the TRIAC to trigger
at a specific voltage
o b) The maximum current the
SCR can conduct. o d) To prevent the TRIAC from
turning off
o c) The minimum current
required to keep the SCR in the Answer: c) To allow the TRIAC to trigger at a
on state. specific voltage

o d) The current required to Performance and Characteristics of

trigger the SCR. Thyristors and SCRs

Answer: c) The minimum current required to

keep the SCR in the on state.
 16.Which of the following factors o b) By clamping voltage spikes
determines the maximum current and limiting the rate of voltage
that an SCR can handle? rise
o a) The gate current o c) By increasing the holding
current
o b) The junction temperature
o d) By providing additional
o c) The anode-to-cathode
current to the load
voltage
Answer: b) By clamping voltage spikes and
o d) The holding current
limiting the rate of voltage rise
Answer: b) The junction temperature
17.What is the effect of increasing
the gate current on the turn-on
time of an SCR?
o a) It decreases the turn-on time.

o b) It increases the turn-on time.

o c) It has no effect on the turn-on

time.
o d) It causes the SCR to turn off.

Answer: a) It decreases the turn-on time.

18.Which of the following is a typical
application of an SCR in power
electronics?
o a) Signal amplification in
communication devices
o b) Controlling the output of a
power supply
o c) Switching RF signals in
antenna systems
o d) Driving a small LED in a
microcontroller circuit
Answer: b) Controlling the output of a power
supply
19.What is the consequence of
exceeding the maximum gate
current rating of an SCR?
o a) The SCR will turn off
immediately.
o b) The SCR will permanently fail.

o c) The SCR will operate more

efficiently.
o d) The SCR's holding current will
increase.
Answer: b) The SCR will permanently fail.
20.How does a snubber circuit
protect an SCR?
o a) By preventing excessive gate
current