Electrical Circuit Breaker Quiz

What is the function of the thermal/magnetic trip units in an MCB?

• To regulate the flow of electricity

• To open the breaker contacts during an overcurrent event

• To convert electrical energy into mechanical energy

• To provide a physical barrier for safety

What is the thermal trip unit sensitive to in an MCB?

• Voltage fluctuations

• Temperature

• Current sensitivity

• Mechanical stress

How do the thermal and magnetic trip units in an MCB act in relation to the breaker's trip mechanism?

• They act independently and mechanically

• They act in unison and electrically

• They act independently and electrically

• They act in unison and mechanically

What is the magnetic trip unit sensitive to in an MCB?

• Temperature changes

• Voltage levels

• Current levels

• Physical obstructions

What is the function of the thermal unit in a circuit breaker?

• It protects against short circuits.

• It heats the bimetal causing it to bend and trip the breaker when there is an overload.

• It creates a magnetic field that attracts the movable armature towards the fixed armature.

• It limits and dissipates the arc energy.

What happens when the magnetic trip unit detects a short circuit?

• The increased current flow heats the bimetal.

• The breaker's contacts are cleaned.

• A magnetic field is created that attracts the movable armature towards the fixed armature, tripping the breaker.

• The arc energy is limited and dissipated.

Why can low-magnitude but long-time over-currents be dangerous?

• They can trip the breaker immediately.

• They can cause the bimetal to cool down.

• They can reduce the life of the electrical installation and may result in fire if left unchecked.

• They increase the tripping time of the breaker.

What is the role of the arc chamber in a circuit breaker?

• It heats the bimetal in case of an overload.

• It creates a magnetic field to attract the armature.

• It protects against overload currents.

• It limits and dissipates the arc energy.

What is the Ampere Rating or Rated Current (In) for a Miniature Circuit Breaker (MCB)?

• The maximum continuous current it can carry for 1 hour

• The maximum uninterrupted current it can withstand at a given ambient temperature without abnormal temperature rise

• The maximum current it can interrupt during a short circuit

• The maximum current it can carry for a specified value of current without tripping

What is the conventional non-tripping current (Iₙt=1,13 Iₙ) for an MCB?

• A specified value of current which the device can carry for a specified time without operating

• The maximum fault current the MCB can interrupt

• The current at which the MCB will trip immediately

• The current the MCB can carry indefinitely without tripping