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ELX > A1 LT12 > Flashcards

A1 LT12 Flashcards

1
Q

What are the two main types of cartridge fuses?

A

Ferrule type and knife-blade type

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2
Q

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

A

Needed to be replaced every time it opened

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3
Q

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

A

Moves midway between ON and OFF

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4
Q

What are the ends of cartridge fuses named after?

A

Shotgun cartridge

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5
Q

How do you reset a tripped breaker?

A

Move from centre to OFF, then to ON

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6
Q

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

A

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

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7
Q

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

A

15 A

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8
Q

What are the types of trip elements in circuit breakers?

A

Thermal and magnetic

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9
Q

How does a fuse protect a circuit?

A

Melts open to break circuit

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10
Q

What is the other name for plug fuses?

A

Screw-in fuse or Edison-base fuse

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11
Q

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

A

20 A

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12
Q

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

A

To protect the circuit from damage

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13
Q

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

A

30 A

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14
Q

How does a fuse operate?

A

Higher resistance alloy with lower melting point

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15
Q

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

A

40 A

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16
Q

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

A

Fuse link begins to melt open.

17
Q

What is the most common type of circuit breaker?

A

Moulded-case circuit breaker

18
Q

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

A

No, it may not always open instantly.

19
Q

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

A

Voltage, current, interrupting capacity, dimensions

20
Q

What triggers a circuit breaker to open?

A

Prolonged overload or excessive current

21
Q

What is a thermal trip element made of?

A

Bimetal strip of two dissimilar metals

22
Q

How can circuit breakers be operated?

A

Magnetic or thermal action

23
Q

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

A

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

24
Q

What are the different configurations of circuit breakers?

A

Single-pole, double-pole, three-pole

25
Q

Are circuit breakers interchangeable among different manufacturers?

A

No

26
Q

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

A

Higher ratings mean larger and longer fuse

27
Q

How are standard circuit breakers rated?

A

In amperes

28
Q

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

A

Auto industry and other specialized industries

29
Q

Where are plug fuses commonly used?

A

Domestic ranges and older installations

30
Q

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

A

The one closest to the fault

31
Q

What is a fuse?

A

Overcurrent device designed to break circuit

32
Q

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

A

Lowest current rating

33
Q

How is selective protection achieved in the circuit?

A

By having higher ampere ratings on upstream breakers

34
Q

What are time-delay fuses?

A

Take more time to melt and open

35
Q

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

A

Manufacturer’s letters

36
Q

Where are fuses used?

A

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

37
Q

What are some standard current ratings for circuit breakers?

A

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

38
Q

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

A

Trip

ELX (55 decks)

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