1. What is the purpose of an actuator in a control system?
a) To generate electrical signals
b) To convert electrical energy into mechanical motion
c) To store mechanical energy
d) To amplify mechanical vibrations
Answer: b) To convert electrical energy into mechanical motion
Explanation: Actuators are devices that convert electrical energy into mechanical motion or force, enabling them to control systems by physically moving or manipulating components.
2. Which of the following is an example of a mechanical switch?
a) Diode
b) Thyristor
c) Relay
d) Transistor
Answer: c) Relay
Explanation: A relay is an electromechanical switch operated by an electrical current. It consists of a coil and a set of contacts that open or close when the coil is energized or de-energized.
3. What is the main issue associated with mechanical switches known as “bouncing”?
a) Overheating
b) Voltage drop
c) Unreliable switching
d) Short circuit
Answer: c) Unreliable switching
Explanation: Mechanical switches can exhibit bouncing, which refers to the rapid opening and closing of contacts when the switch is actuated. This can lead to unreliable switching behavior and false signals.
4. Which method is commonly used to prevent bouncing of mechanical switches?
a) Increasing voltage
b) Decreasing current
c) Debouncing circuits
d) Adding resistance
Answer: c) Debouncing circuits
Explanation: Debouncing circuits are commonly used to filter out bouncing signals from mechanical switches, ensuring smooth and reliable operation.
5. Which electrical component is known for its use in preventing reverse current flow in circuits?
a) Diode
b) Thyristor
c) Triac
d) Transistor
Answer: a) Diode
Explanation: Diodes are semiconductor devices that allow current to flow in one direction only, making them useful for preventing reverse current flow in circuits.
6. What is the main principle behind the operation of solenoids?
a) Electromagnetic induction
b) Piezoelectric effect
c) Capacitive coupling
d) Quantum tunneling
Answer: a) Electromagnetic induction
Explanation: Solenoids operate on the principle of electromagnetic induction, where a current flowing through a coil of wire generates a magnetic field, which in turn produces mechanical motion when interacting with a ferromagnetic core.
7. Which type of motor is commonly used in applications requiring precise control of position and speed?
a) DC motor
b) Stepper motor
c) AC motor
d) Servo motor
Answer: d) Servo motor
Explanation: Servo motors are used in applications requiring precise control of position and speed due to their ability to maintain a set position and respond accurately to control signals.
8. What is the primary function of pressure relief valves in hydraulic systems?
a) To increase pressure
b) To decrease pressure
c) To regulate flow
d) To prevent overpressure
Answer: d) To prevent overpressure
Explanation: Pressure relief valves in hydraulic systems are designed to prevent overpressure by opening when the pressure exceeds a certain threshold, diverting excess fluid flow and relieving pressure.
9. Which type of valve is commonly used for precise control of fluid flow in hydraulic systems?
a) Needle valve
b) Globe valve
c) Relief valve
d) Check valve
Answer: a) Needle valve
Explanation: Needle valves are used for precise control of fluid flow in hydraulic systems due to their fine adjustment capability, achieved by a long, tapered needle-like plunger.
10. What type of valve is commonly used for controlling the direction of fluid flow in hydraulic systems using solenoids?
a) Ball valve
b) Gate valve
c) Sliding spool valve
d) Butterfly valve
Answer: c) Sliding spool valve
Explanation: Sliding spool valves are commonly used for controlling the direction of fluid flow in hydraulic systems using solenoids. They consist of a cylindrical spool that slides within a housing to open or block fluid passages.
11. Which of the following is NOT a classification of actuator system?
a) Hydraulic
b) Pneumatic
c) Mechanical
d) Magnetic
Answer: d) Magnetic
Explanation: Actuator systems are commonly classified into hydraulic, pneumatic, and mechanical types based on their operating principles and the type of energy they utilize for motion control. “Magnetic” is not typically considered a classification for actuator systems.
12. Which type of motor operates on the principle of commutation to maintain continuous rotation?
a) Stepper motor
b) AC motor
c) Brushed DC motor
d) Brushless DC motor
Answer: c) Brushed DC motor
Explanation: Brushed DC motors rely on a commutator mechanism to switch the direction of current flow through the motor windings, ensuring continuous rotation of the motor shaft.
13. What is the primary function of a pressure regulating/reducing valve in hydraulic systems?
a) To increase pressure
b) To decrease pressure
c) To regulate flow
d) To prevent leakage
Answer: b) To decrease pressure
Explanation: Pressure regulating/reducing valves in hydraulic systems are designed to decrease or regulate pressure in a fluid circuit to a specified level, ensuring stable operation of downstream components.
14. Which electrical component acts as a semiconductor switch, allowing current to flow only when triggered by a control signal?
a) Diode
b) Thyristor
c) Transistor
d) Relay
Answer: c) Transistor
Explanation: Transistors are semiconductor devices that can act as switches, controlling the flow of current between two terminals based on the input voltage or current applied to a third terminal.
15. Which type of valve is commonly used for on/off control of fluid flow in hydraulic systems?
a) Needle valve
b) Globe valve
c) Ball valve
d) Check valve
Answer: c) Ball valve
Explanation: Ball valves are commonly used for on/off control of fluid flow in hydraulic systems due to their simple design and reliable operation, where a spherical closure element controls flow by rotating within a valve body.
16. What is the purpose of a solenoid in an actuator system?
a) To generate mechanical motion
b) To regulate fluid pressure
c) To convert electrical
energy into mechanical motion
d) To control direction of fluid flow
Answer: c) To convert electrical energy into mechanical motion
Explanation: Solenoids are electromechanical devices that convert electrical energy into mechanical motion. They typically consist of a coil of wire wound around a ferromagnetic core, which produces a magnetic field when energized, causing the core to move and perform mechanical work.
17. Which type of motor is commonly used in applications requiring precise control of angular displacement in discrete steps?
a) AC motor
b) DC motor
c) Stepper motor
d) Servo motor
Answer: c) Stepper motor
Explanation: Stepper motors are widely used in applications requiring precise control of angular displacement in discrete steps, where each step corresponds to a specific position. They are commonly found in printers, CNC machines, and robotic systems.
18. What is the primary function of a pressure sequence valve in hydraulic systems?
a) To increase pressure
b) To decrease pressure
c) To regulate flow
d) To control sequence of operations
Answer: d) To control sequence of operations
Explanation: Pressure sequence valves in hydraulic systems are used to control the sequence of operations by allowing fluid flow to a downstream circuit only when a specified pressure level is reached in the upstream circuit.
19. Which type of solid-state switch is commonly used for controlling large AC loads such as electric motors?
a) Diode
b) Thyristor
c) Transistor
d) Darlington pair
Answer: b) Thyristor
Explanation: Thyristors, also known as silicon-controlled rectifiers (SCRs), are solid-state switches commonly used for controlling large AC loads such as electric motors, due to their ability to handle high current and voltage levels.
20. Which type of actuator system utilizes the pressure of compressed air to generate mechanical motion?
a) Hydraulic
b) Pneumatic
c) Mechanical
d) Magnetic
Answer: b) Pneumatic
Explanation: Pneumatic actuator systems utilize the pressure of compressed air to generate mechanical motion, making them suitable for applications where precise control, rapid response, and cleanliness are required. They are commonly used in industries such as manufacturing, automotive, and aerospace.