A1 LT12

Question 1

What are the two main types of cartridge fuses?

Answer 1

Ferrule type and knife-blade type

Question 2

What was the disadvantage of the fuse that led to the search for an alternative method?

Answer 2

Needed to be replaced every time it opened

Question 3

What happens to the breaker’s handle when it trips?

Answer 3

Moves midway between ON and OFF

Question 4

What are the ends of cartridge fuses named after?

Answer 4

Shotgun cartridge

Question 5

How do you reset a tripped breaker?

Answer 5

Move from centre to OFF, then to ON

Question 6

What is the difference between ferrule and knife-blade type cartridge fuses?

Answer 6

Knife-blade type is used for fuses rated above 60 A

Question 7

What size of circuit breaker is typically used for lights and plugs in domestic settings?

Answer 7

15 A

Question 8

What are the types of trip elements in circuit breakers?

Answer 8

Thermal and magnetic

Question 9

How does a fuse protect a circuit?

Answer 9

Melts open to break circuit

Question 10

What is the other name for plug fuses?

Answer 10

Screw-in fuse or Edison-base fuse

Question 11

What size of circuit breaker is usually used for heaters in domestic settings?

Answer 11

20 A

Question 12

Why are fuses designed to be the weakest link in an electric circuit?

Answer 12

To protect the circuit from damage

Question 13

What size of circuit breaker is commonly used for clothes dryers in domestic settings?

Answer 13

30 A

Question 14

How does a fuse operate?

Answer 14

Higher resistance alloy with lower melting point

Question 15

What size of circuit breaker is typically used for ranges in domestic settings?

Answer 15

40 A

Question 16

What happens when the current level exceeds the fuse’s rating?

Answer 16

Fuse link begins to melt open.

Question 17

What is the most common type of circuit breaker?

Answer 17

Moulded-case circuit breaker

Question 18

Is a fuse guaranteed to open instantly when its rating is exceeded?

Answer 18

No, it may not always open instantly.

Question 19

What characteristics do the identification letters on the circuit breaker frame refer to?

Answer 19

Voltage, current, interrupting capacity, dimensions

Question 20

What triggers a circuit breaker to open?

Answer 20

Prolonged overload or excessive current

Question 21

What is a thermal trip element made of?

Answer 21

Bimetal strip of two dissimilar metals

Question 22

How can circuit breakers be operated?

Answer 22

Magnetic or thermal action

Question 23

Why does a fuse open almost instantly on heavy fault current but more slowly on overload current?

Answer 23

Time to melt and open is inversely proportional to current magnitude.

Question 24

What are the different configurations of circuit breakers?

Answer 24

Single-pole, double-pole, three-pole

Question 25

Are circuit breakers interchangeable among different manufacturers?

Answer 25

No

Question 26

How do amperage and voltage ratings affect the size of a fuse?

Answer 26

Higher ratings mean larger and longer fuse

Question 27

How are standard circuit breakers rated?

Answer 27

In amperes

Question 28

In which industries are circuit breakers with lower current ratings often used?

Answer 28

Auto industry and other specialized industries

Question 29

Where are plug fuses commonly used?

Answer 29

Domestic ranges and older installations

Question 30

According to Figure 5, which circuit breaker should trip first when a fault occurs?

Answer 30

The one closest to the fault

Question 31

What is a fuse?

Answer 31

Overcurrent device designed to break circuit

Question 32

How are the circuit breakers protecting branch circuits rated compared to upstream breakers?

Answer 32

Lowest current rating

Question 33

How is selective protection achieved in the circuit?

Answer 33

By having higher ampere ratings on upstream breakers

Question 34

What are time-delay fuses?

Answer 34

Take more time to melt and open

Question 35

How are different types of moulded cases identified on the frame by manufacturers?

Answer 35

Manufacturer's letters

Question 36

Where are fuses used?

Answer 36

Homes, offices, industry, automobiles, ships, electronic equipment

Question 37

What are some standard current ratings for circuit breakers?

Answer 37

15, 20, 30, 40, 50, 60, 70, 100 A

Question 38

What should happen if a fault develops in the branch circuit?

Answer 38

Trip