303 #3 – Protective Devices

What is the main purpose of a fuse?

• To detect smoke

• To prevent electrical fires by controlling voltage

• To disconnect a circuit under fault conditions

• To reduce energy usage

Which of the following is designed to protect people from electric shock?

• MCB

• RCBO

• RCD

• BS3036 fuse

Which of these is classed as a protective device?

• Junction box

• Cable tray

• RCD

• Earth rod

What is the difference between isolation and switching?

• Isolation is temporary, switching is permanent

• Isolation is for safety; switching is for control

• Switching is only used in ring circuits

• Isolation is only for lighting

Which regulation in BS7671 covers isolation and switching?

• Chapter 41

• Chapter 52

• Chapter 53

• Chapter 54

A device that provides both overcurrent and earth fault protection is called:

• RCD

• RCBO

• Isolator

• SPD

What is coordination in electrical protection?

• Matching cable sizes

• Ensuring devices operate in sequence during faults

• Aligning conduits

• Keeping all circuits equal

Which device trips the fastest under high fault current?

• Type B MCB

• Type C MCB

• Type D MCB

• Fuse wire

A lock-off kit is used when:

• Testing insulation

• Working on live circuits

• Isolating a circuit for maintenance

• Earth bonding a pipe

What does MCB stand for?

• Mechanical Circuit Breaker

• Main Control Board

• Miniature Circuit Breaker

• Multiple Conductor Box