Safety Devices and Control Panels — MCQs – EE

1. The primary purpose of electrical safety devices is to:
(A) Protect equipment and personnel from faults and hazards
(B) Increase power factor
(C) Improve voltage regulation
(D) Control frequency

2. A fuse is a safety device that:
(A) Protects circuits from overcurrent conditions
(B) Regulates voltage
(C) Improves load balancing
(D) Controls reactive power

3. A circuit breaker is used to:
(A) Automatically interrupt current flow under fault conditions
(B) Manually switch off circuits only
(C) Step up voltage
(D) Act as a capacitor

4. The operating principle of a fuse is based on:
(A) Heating effect of current
(B) Magnetic induction
(C) Capacitance
(D) Resonance

5. A miniature circuit breaker (MCB) provides protection against:
(A) Overload and short circuit
(B) Only overvoltage
(C) Power factor drop
(D) Earth fault only

6. A residual current device (RCD) protects against:
(A) Earth leakage current
(B) Overcurrent
(C) Voltage surges
(D) Frequency changes

7. An overload relay is designed to:
(A) Protect motors from prolonged overcurrent
(B) Measure voltage
(C) Prevent surge voltage
(D) Start the motor

8. A thermal overload relay works on the principle of:
(A) Heating due to excessive current
(B) Magnetic induction
(C) Optical sensing
(D) Voltage control

9. An earth leakage circuit breaker (ELCB) operates when:
(A) Leakage current flows to earth
(B) Load current increases
(C) Power factor improves
(D) Voltage drops

10. A surge protector is used to:
(A) Protect equipment from voltage spikes and transients
(B) Increase system current
(C) Improve insulation resistance
(D) Block DC components

11. A control panel is used to:
(A) Centralize control and monitoring of electrical circuits
(B) Increase circuit voltage
(C) Step up current
(D) Replace transformers

12. The main components of a control panel include:
(A) Circuit breakers, contactors, relays, and meters
(B) Batteries only
(C) Motors and transformers only
(D) Heating elements only

13. A contactor is used to:
(A) Switch high current loads using low power control signals
(B) Measure voltage
(C) Limit current
(D) Step up voltage

14. Control panels are typically made of:
(A) Mild steel or stainless steel
(B) Plastic only
(C) Wood
(D) Copper

15. The MCC panel stands for:
(A) Motor Control Center
(B) Main Control Cabinet
(C) Machine Circuit Controller
(D) Motor Current Controller

16. The PCC panel stands for:
(A) Power Control Center
(B) Phase Control Cabinet
(C) Power Conversion Center
(D) Phase Current Controller

17. The function of an MCC panel is to:
(A) Control and protect electric motors
(B) Measure energy consumption
(C) Store energy
(D) Distribute DC power

18. Control panels in industries are usually designed to operate on:
(A) Three-phase AC supply
(B) Single-phase DC supply
(C) High-frequency AC
(D) Low-voltage DC

19. The emergency stop button in a control panel is used to:
(A) Instantly disconnect power supply during emergencies
(B) Reset the panel
(C) Start the motor
(D) Measure insulation resistance

20. The color of the emergency stop button is generally:
(A) Red
(B) Green
(C) Yellow
(D) Blue

21. Indicator lamps on a control panel show:
(A) Status of circuits such as ON, OFF, or fault conditions
(B) Supply frequency
(C) Load impedance
(D) Phase angle

22. A push button switch is used for:
(A) Manually controlling operations such as start and stop
(B) Measuring voltage
(C) Overcurrent protection
(D) Load balancing

23. A relay in a control panel functions as:
(A) An automatic switch operated by an electrical signal
(B) A voltage regulator
(C) A current limiter
(D) A mechanical interlock

24. The purpose of control wiring in a panel is to:
(A) Carry control and signaling currents
(B) Carry main power
(C) Increase resistance
(D) Reduce current

25. A control transformer in a panel is used to:
(A) Step down voltage for control circuits
(B) Step up current
(C) Improve power factor
(D) Filter harmonics

26. The overload protection in a control panel is provided by:
(A) Thermal relays or MCBs
(B) Voltage stabilizers
(C) Capacitors
(D) Switch fuses

27. Control panels are designed according to standards such as:
(A) IEC 61439 or IS 8623
(B) IEEE 519
(C) ISO 14001
(D) ASTM 303

28. Earthing of a control panel ensures:
(A) Operator safety and fault current dissipation
(B) Better power factor
(C) Load balancing
(D) Increased current capacity

29. The busbars in control panels are typically made of:
(A) Copper or aluminum
(B) Iron
(C) Steel
(D) Plastic

30. The main objective of safety devices and control panels is to:
(A) Ensure safe operation, monitoring, and protection of electrical systems
(B) Increase system losses
(C) Operate circuits manually
(D) Reduce voltage levels